Internal conulariid structures unveiled using µCT

PalZ https://doi.org/10.1007/s12542-023-00649-7 RESEARCH PAPER Internal conulariid structures unveiled using µCT Consuelo Sendino1 · Brett Clark2 · André C. Morandini3,4 · Tobias Salge2 · Miranda Lowe5 · Willian Rushlau6 Received: 31 May 2022 / Accepted: 1 February 2023 © Crown 2023 Abstract An extensive sample of well-preserved conulariids from the Pennsylvanian of the North American Midcontinent (Texas and Oklahoma, USA) have been studied using X-ray micro-Computed Tomography (µCT) and have shown structures identified as longitudinal muscle bundles and a potential gastric cavity. These unequivocal structures appear in several specimens coming from different sites. Their preservation varies from a gastric cavity with muscle bundles in some individuals to only longitudinal muscle bundles in others. The muscle bundles fuse apically or medially, normally forming V-shaped pairs, and they extend along the theca/exoskeleton, parallel to the corner, towards the aperture. Longitudinal bundles have predominant perradial positions. Although there have been some articles on conulariid soft parts, most of them refer to relic soft parts. This is the first time that these structures are shown using µCT. Discovery of conulariid soft parts contributes to knowledge of metazoan evolutionary history. Keywords Conulariid · Internal structure · Soft parts · Pennsylvanian · Texas · Oklahoma · µCT · Scyphozoa · Coronatae Introduction with respect to their soft parts. It has been assumed that soft parts can be inferred from preserved hard parts, but proper Conulariids have been studied for more than two centu- soft part anatomy has never been documented. ries, since the first time that a Carboniferous specimen was Although Barrande (1855a, b, 1867) already highlighted figured by “the father of Scottish palaeontology”, Rever- the conulariid organic deposit had to build the schott, the end David Ure, in 1793 (pl. 20: Fig. 7). Since then, when first authors to speculate about conulariid soft parts were conulariids were referred to as “very rare” (Ure 1793: p. Bouček and Ulrich (1929 : p. 206) when they inferred that 331) until the present, much progress has been made in the the muscles, which closed and opened the aperture, could study of the group’s external morphology, but very little only be attached to internal septa. Some years later, Kid- erlen (1937) was the pioneer in describing conulariid relic Handling Editor: Mike Reich. soft parts in detail, elucidating muscular attachments in the aperture. After observing numerous specimens from differ- * Consuelo Sendino ent sites around the world and some of them with several c.sendino-lara@nhm.ac.uk schotts, Kiderlen (1937) came to the conclusion the soft 1 Department of Earth Sciences, The Natural History body was firmly attached to the theca and completely lined it Museum, London, UK with its “epithelium”, with the exception of the aboral area. 2 Core Research Laboratories, The Natural History Museum, He also described how the aperture could have only been London, UK closed by muscle contraction, these muscles being attached 3 Departamento de Zoologia, Instituto de Biociências, to the septa and also responsible for the ribs’ alternation, or Universidade de São Paulo, Rua do Matão, Travessa 14, not, at the midline. Kiderlen’s concepts were fundamental n. 101, SP 05508‑090 São Paulo, Brazil to support a cnidarian affinity for the conulariids and have 4 Centro de Biologia Marinha, Universidade de São been echoed until nowadays. Paulo, Rod. Manoel Hipólito do Rego km 131.5, Moore and Harrington (1956), in the Treatise on Inverte- SP 11612‑109 São Sebastião, Brazil brate Paleontology, also made inferences on the origin of the 5 Department of Life Sciences, The Natural History Museum, soft parts responsible for building the theca, writing about London, UK its ectodermal origin. This was based on observations of 6 2706 North 382, Wetumka, OK 74883, USA 13 Vol.:(0123456789)  C. Sendino et al. individuals with encrusting organisms on their four faces, tissue, probably muscle bands that would have been attached but maintaining erect positions when they were alive. If the to corner carinae. The presence of this structure in conu- theca had an endodermal origin, it would have been secreted lariids becomes really meaningful and will be compared to covering the external parts and none of the encrusters could recent cnidarian groups in a consecutive paper. Most of these have been attached. A few years later, Werner (1966, 1967, specimens show an almost perfect radial tetramerous sym- 1971) compared the relic soft parts of conulariids to coro- metry of their thecae. nate scyphozoan polyps, interpretating conulariids as tentac- ulate animals, as Kiderlen (1937) and Moore and Harrington (1956) did as well. Geological setting The end of the twentieth century was the peak moment of the study of fossils using X-rays. Steul (1984) used X-ray The specimens described in this paper were collected from radiographs to study conulariids from the Hunsrück Slate, the Pennsylvanian of the North American Midcontinent Lower Devonian of SW Germany. She described and illus- (Fig. 2), in Central Oklahoma and North-Central Texas trated putative soft parts seen through X-Ray, but unfortu- (USA). This area has been well-studied stratigraphically due nately was misled by a nautiloid siphuncle (see Hergarten to the perspective of regional exploration for hydrocarbon 1994 for explanation) and the rest of the specimens could not reserves. Pennsylvanian strata in this area are dominated by be re-examined as their origin and whereabouts are mostly transgressive–regressive lithic sequences, or cyclothems unknown. (Heckel 1991). Maximum transgression is characterised by Babcock and Feldmann (1986b: Fig. 30.5) illustrated deposition of organic-rich black mud. one of eight specimens from the Lower Mississippian of The Middle–Upper Pennsylvanian stratigraphic sequence Kentucky and Alberta, studying soft remains using X-ray in the Midcontinent formed north of the equator in the trop- radiographs. They also showed images of specimens with ical trade wind belt of that time. Though deposition was remains of soft parts. They described and drew them as a generally slow in the North America Midcontinent during single elongate tube and globular masses (Babcock and this age, it was more rapid near active detrital sediment Feldmann 1986a). The elongate structure is always located sources, particularly in central Oklahoma. The conulariids near a corner, extending most of the theca length and turning were found in the fissile black shale (Malinky and Heckel at an angle of almost 90° to the long axis of the theca close 1998), in the offshore part of the Pennsylvanian cyclo- to the aperture. They interpretated the longitudinal structures thems. This shale indicates dysoxic conditions rather than as remains of organ systems. These researchers were the fully anoxic conditions that prevailed at least on the seafloor first ones to illustrate presumed soft parts. Much later, Van from time to time. This should be the reason for the low Iten and Südkamp (2010) also studied Hunsrück conulariids biodiversity found in these levels, probably with an oxy- with X-rays and observed irregular concentrations of pyrite, gen content between 0.7 and 0.3 ml/l (Demaison and Moore some oriented more or less parallel to a midline or corner or 1980) that would be maintained during long periods. The obliquely to the specimen’s long axis, close to the aperture, Wewoka and Graham formations from Central Oklahoma but without a clear structure, assuming these concentrations and North Texas, respectively, (Fig. 3) have harvested hun- were decayed remains of soft parts. dreds of specimens that we have studied for this research. Special mention is deserved for a recent publication by Some of these were collected near Atwood, Hughes County, Miller et al. (2022). This research is based on scanning elec- probably in the Lower Wewoka Member, in what has been tron microscopy (SEM) with energy-dispersive spectrometry named beds of less resistant shales (Weaver 1954). The pal- (EDS) of Silurian Waukesha Lagerstätte conulariids. These aeoenvironment of these shales probably included turbidity specimens underwent a complex taphonomic history that did currents which carried fine-grained material. These deposits not leave clear soft parts preserved, but kerogenized patches have been able to preserve what we consider soft parts of an and carbon films within the theca remains, assuming these abundant and low diversity population of individuals which kerogenized patches could have been derived from decayed suffered from predation. Some of the individuals studied organic material. from both Pennsylvanian sites have evidence of bioturba- Therefore, this is the first time that assumed internal tion, which means the sea bottom was not hostile to life at structures of conulariids are seen using µCT. Here we report least intermittently. on the most complete, and best preserved specimens in three Hughes County is on the southeast edge of the central dimensions of conulariids from the Wewoka and Graham Oklahoma uplift, with thick deposits of lower Desmoine- formations, Pennsylvanian, of Oklahoma and Texas, USA sian age which were deposited in a shallow sea covering (Fig. 1), respectively. These fossils show a distribution of this basin. Outcrops of middle and upper Desmoinesian age longitudinal bundles inside of the theca, from the proximal- are spread throughout this county. Close to the Canadian to-distal regions, and what we consider remains of muscle River Valley, near Atwood and Holdenville Lake, there are 13 Internal conulariid structures unveiled using μCT Fig. 1  General view (A, C) and apertural view (B, D) of Paraconularia sp. NHMUK PI CL 616 from Finis Shale Member of Texas and ‘Conu- laria crustula’ NHMUK PI CL 632 from Middle Wewoka Member of Oklahoma friable sandstones and shales, mostly massive, alternating site (Fig. 2a close to Jacksboro Lake) with fossils in excep- beds of about 200 m thickness (Weaver 1954) that conform tional conditions, mostly found in situ, in black to dark-grey to the Wewoka Formation. The shales are by far the more shale, with siderite nodules as well. The Finis Shale fauna dominant lithology. The fossiliferous clay shales that house is considered one of the best sampled and preserved fos- the conulariids can be seen in the Lower and Middle mem- sil assemblages known to science. Conulariids appear in bers. The Middle Wewoka Member shales stand out for the the Crurithyris-Paraconularia Community of Lobza et al. abundant and perfectly preserved fossil shells of brachiopods (1994), in a relatively firm mud bottom with shallow water and molluscs (Weaver 1954; West 1970) that can be also depths changing to deeper and calm water conditions. The extended to the conulariid thecae. Numerous fossil sponges, fact of the relatively small number of individuals per species echinoderms, bryozoans, trilobites, corals, fishes and plants and their size, larger than in overlying deposits, suggests a have been very well preserved as well. As the sandstones and high rate of sedimentation. The energy for the transport was shales may be discontinuous in many areas, intertonguing probably low. Although anoxic conditions within the sub- with the overlying and underlying shales, we are not sure if strate are evident from the pyritic preservation of fossils, the some of the conulariids collected near Atwood belong to the abundance of preserved organic matter and the few infaunal Lower Wewoka Member (marked with a question mark on species suggest overlying water was oxygenated. Fig. 3). The lower part of the Graham Formation, the Finis The Pennsylvanian area of North-Central Texas has Shale, is very well exposed at the Lost Creek Lake spillway been described in reference to the sedimentary formations 13  C. Sendino et al. of the Midcontinent as two great inliers of Carboniferous sediments that protrude through Cretaceous strata on the east and dip beneath Permian rocks on the west and north of North-Central Texas (Plummer 1919). In the vicinity of Jacksboro, Jack County, there are rocks which are part of the Canyon and Cisco groups of Pennsylvanian age. The Cisco Group was deposited during increased orogenic activ- ity in the mid-continent. Its deposition was controlled by the complex interaction of delta progradation, basin sub- sidence, shift stability and terrigenous clastic input from the surrounding mountains to the east in conjunction with eustatic sea-level fluctuations derived from glaciations in Gondwana (McLeod et al. 2003). It involves the north-west one-third of the county. The basal Cisco Group outcrops near Lost Creek Reservoir Spillway, at the north end of Lake Jacksboro (northeast of Jacksboro city), contain the Finis shales (Fig. 3; lower section of the Graham Formation, Upper Pennsylvanian), very prolific in well-preserved fos- sils. It has a thickness of about almost 10 m. The Finis Shale has been interpreted to be the deep-water shale component of a typical Midcontinent cyclothem (Boardman et al. 1984). A cyclothem sequence usually consists of, from base to the top, a nearshore shale, a transgressive limestone, a deep- water shale, a regressive limestone and another nearshore shale. At the base, phosphatic, black shales were deposited in anoxic waters below a thermocline, with a high rate of organic decomposition and bacterial interaction. At this level there are mostly pelagic and nektonic remains, and occa- Fig. 2  Geographical location of the collecting sites sional presence of conulariids, meaning that dysoxic, instead Fig. 3  Pennsylvanian time scale with correspondence with the regional stages and conulariid occurrences 13 Internal conulariid structures unveiled using μCT of anoxic, conditions prevailed on the seafloor from time Sendino 2021: Fig. 9 for explanation on open nomencla- to time (Malinky and Heckel 1998). Overlying the phos- ture here) from the Silurian of Dudley, Worcestershire phatic black shales are medium to dark gray shales, normally (UK), and the Carboniferous of East Renfrewshire (Scot- deposited under shallower oxygenated waters with high land) have been studied. The reason for studying these biodiversity (Boardman et al. 1984). Low current activity individuals is because they are the best preserved speci- and sedimentation rates allowed good preservation in situ. mens in the Conulariida collection at the Natural History Finally, towards the top of the Finis Shale, there are medium Museum, London (NHMUK), preserving their original to light gray shales that are highly fossiliferous, with pyriti- three-dimensional shape and aperture, making them can- sation of some specimens. The paleofauna found at this level didates to study with Micro-CT scanning. All this material is typical of shallower water deposition (Kocurko 1993), used in this study is deposited in the NHMUK. restricted to shallow-shelf muddy siliciclastic sediments. We made a selection of the best specimens, because they This makes the lower Virgilian Finis Shale one of the most preserve the aperture or keep the most external layer of the richly fossiliferous exposures of marine shelf sediments in theca, or because they have an unusual structure, such a the United States (McLeod et al. 2003) and they have yielded conulariid theca inside of another conulariid theca (Fig. 4), more than 100 conulariids of the same species. The best which was already reported in living coronates (Morandini preserved specimens, 74 individuals, have been studied. The and Jarms 2010). A total of 60 individuals from the Pennsyl- other upper half of the outcrop is also fossiliferous, but with vanian of the North American Midcontinent and two from thin discontinuous sandstones lenses. Silurian and Carboniferous of England and Scotland, respec- tively, were chosen, which were firstly radiographed in order to make another selection with those candidates to show soft Materials and methods parts (Fig. 5). The specimens studied here were unprepared except for mechanical removal of minor amounts of rock This study is based mainly on material collected from the matrix. 33 individuals were scanned with Carl Zeiss Xradia Wewoka and Graham formations, Pennsylvanian, of Okla- Versa 520 Micro-CT scanner, which combines classic X-ray homa and Texas, USA. A total of 298 isolated specimens of geometric magnification with different optical lenses. They ‘Conularia crustula’ (White 1880) from the Wewoka For- were analysed at a range of source conditions; 60 to 160 kV mation and Paraconularia sp. from the Graham Formation, (adjusted depending on specimen size). Data were recon- all preserved in three dimensions, have been studied. ‘Conu- structed using the ZEISS software from 1601 to 3201 projec- laria crustula’ is common in the Carboniferous of Texas tions taken over 360°. The reconstructed images were then and Oklahoma. Most of the specimens are small, a few cen- segmented and rendered using Avizo software (ver. 2019.1 timetres in length as adults. Although C. crustula has been Amira-Avizo, Thermo Fisher Scientific, USA), highlighting traditionally assigned to the genus Paraconularia by many the internal structures in different colours. palaeontologists, White (1880: p. 170, 1881: p. XXVIII) For scanning electron microscopy (SEM) and energy- described this species with transverse ribs that cross the dispersive X-ray spectrometry (EDS), selected samples sulcate corners, bending slightly adaperturally (“striae were embedded in epoxy resin, cut, polished and coated …. across the angle-furrows, in crossing which they bend with 10 nm carbon. A ZEISS EVO LS15 SEM and Oxford slightly backward”). Consequently, if the transverse ribs are Instruments AZtec EDS system with an XMax 80 ­mm2 not interrupted at the sulcate corners as White’s (1880: pl. silicon drift detector was operated at an accelerating volt- 42: Fig. 4a, 1881: pl. 3: Fig. 4a, 4b) illustrations showed, this age of 20 kV and a probe current of 1.5 nA resulting in an species would not belong to Paraconularia Sinclair, 1940. output count rate of ~ 50,000 counts per seconds. A large We therefore recommend redescribing this species after area elemental map was acquired for one sample. 120 fields examining the type specimens and will name these speci- were acquired using automated stage control. Each field cov- mens under open nomenclature as ‘Conularia crustula’. The ered an area of 563 × 422 μm and was analysed for ~ 25 min. Finis Shale specimens are smaller, with lower apical angle, Secondary electron (SE) and back-scattered electron (BSE) and whose transverse ribs are interrupted in the corners. We images were acquired at a resolution of 1024 × 768 pix- did not find any species already described which fit with our els, corresponding to a pixel size of 0.55 μm. EDS spectra specimens from the Finis Shale. were stored as hyperspectral imaging datasets at a resolu- The North American specimens were distributed tion of 512 × 384 pixels, corresponding to a pixel size of between the Wewoka Formation (168) and the Graham 1.1 μm. AZtec 5.1 software was used to stitch the individual Formation (130). All these North American specimens fields into one hyperspectral imaging dataset with an EDS have been collected and donated to the Natural History resolution of 5511 × 2984 pixels and SEM resolution of Museum, London, by one of the authors (WR). Two addi- 11,023 × 5968 pixels. The distribution of elements is dis- tional individuals of Paraconularia ‘quadrisulcata’ (see played as net intensity maps where the X-ray background 13  C. Sendino et al. Fig. 4  Incomplete individual (NHMUK PI CL 604) with a predation mark (white arrow) (A) and soft parts protrud- ing from the interior of the theca (B). Probably the theca preserved in the interior of the largest grew inside the latter Fig. 5  Specimen NHMUL PI CL 639, ‘Conularia crustula’ from Middle Wewoka Member of Oklahoma. A General view of the individual and B Seen under X-ray showing soft tissue remains 13 Internal conulariid structures unveiled using μCT has been subtracted and peaks with overlapping X-ray lines the apical part or at the middle of the theca length and ends have been deconvolved. at the aperture hinge level. The width of each branch of the Most of the images shown in this article (except SEM and bundle is about 1.5 mm. These bundles can be intercon- EDS images), from µCT and macrophotographs under inci- nected with possible muscular fibers that extend between dent natural illumination, have been edited in Adobe Pho- bundles (Fig. 7d). Retraction of this muscular system had to toshop CS6. The macrophotographs were obtained using a facilitate closure of the aperture. Canon 5Drs camera mounting 100 mm and Sigma 50-mm Four additional specimens have a similar structure to that lens. All the data can be seen as Supplementary material. shown by Babcock and Feldmann (1986b: figs. 30.2–30.3, 30.5–30.6), with a main longitudinal structure that at the middle of the theca length widens and turns adaperturally. It Description runs in a tubular shape from the apical part to the middle of the theca where it widens to an oval-shape and narrows again Thirty-two individuals, from both North America Midcon- at its end, before the hinge level (Fig. 7a). At the adapical tinent sites, have internal structures susceptible to be conu- area, it is 1 mm wide and at the middle of the theca the width lariid soft parts, after discarding specimens that were heavily is at least three times more. All of these specimens show bioturbated (Fig. 6a), and others with sand grains (Fig. 6b) injuries (NHMUK PI CL 602; CL 613; CL 803; and CL 855) and further bioturbated with remains of soft parts (Fig. 6c). (Fig. 7a, b and Suppl. material) and are originally mostly As these longitudinal structures are common in the scanned from the Finis Shale except the last one cited, NHMUK PI individuals and appear in both the Wewoka and Graham for- CL 855 from the Wewoka. mations, they are not considered to be taphonomic artifacts. A specimen from the Finis Shale (NHMUK PI CL 601: They are also consistent with previous studies considering Fig. 8) preserves four longitudinal bundles that divert from conulariids as scyphozoan polyps. the apical part (Fig. 8). This specimen is displayed on its Ten of these individuals, all of them scanned, have a lon- four sides showing how these four bundles are distributed gitudinal structure in “V” inside the theca cavity, occasion- and how they start to fuse and divert towards the apertural ally with one of the branches more accused than the other, area, keeping a parallel-like position to the corners and not running parallel to the internal theca sides or can be seen to the midline. They are closer to the external side of the with a more central position in the theca (Fig. 7c, d). These theca adaperturally and more distant adapically due to the individuals have mostly damaged thecae, probably due to theca’s thickness. As the theca is thicker adapically, the bun- sublethal and lethal injuries. The “V” structure can start at dles are more distant from the external layer of the theca Fig. 6  Individuals of Paraconularia sp. from Finis Shale Member of CL 810. C With bioturbation and remains of longitudinal bundles, Texas under X-ray and µCT. A Very bioturbated specimen, NHMUK NHMUK PI CL 611 PI CL 606. B Specimen with sand grains in its interior, NHMUK PI 13  C. Sendino et al. Fig. 7  Different structures seen under µCT. A Longitudinal bundles dles with a third bundle partially preserved, NHMUK PI CL 812. E and oval-shaped structure, NHMUK PI CL 602. B Unique longitu- V-shaped longitudinal bundle, NHMUK PI CL 808. A, C & D and E dinal bundle preserved extending adaperturally and part of another individuals of Paraconularia sp. from Finis Shale Member of Texas. bundle, NHMUK PI CL 855. C & D V-shaped longitudinal bun- B ‘Conularia crustula’ from Middle Wewoka Member of Oklahoma or periderm, opposite to the adapertural part with thinner bundles of the conulariid are hardly preserved, with fri- theca. On the other hand, the bundles are thinner adapically able tissue left. These pellets have different sizes and do not (approx. 1 mm wide) and thicker adaperturally (approx. keep any arrangement. They may be faecal pellets that are 1.5 mm). It seems they extend adaperturally to form a layer. not related to the organism with which they are associated. This individual shows a sublethal scar that has been repaired They could be produced by scavengers that fed on soft parts with transverse ribs, partly preserved in its apical part, and (Bruthansová and Kraft 2003) after the death of the conu- other lethal injuries close to the aperture (Fig. 8 with arrows lariid, or by animals which used the empty theca as a hiding showing the injuries). Both of these scars are of puncture place. Observations on living coronates show some annelid type, with a circle-like outline. It is possible to see under CT worms, crustaceans and pycnogonids can feed on the soft scan that soft tissues are behind the injury marks. A couple tissues, oftentimes using the periderm tube (exoskeleton) of of individuals have foraminifera and sponge spicules inside the polyps as a hiding place (ACM, personal observations). their theca remains (e.g. NHMUK PI CL 803, Suppl. mate- As the soft part remains are not well defined, we believe rial), also with bivalve shells, and a brachiopod shell. They that the theca was used as shelter. The animal used the theca could be introduced during a storm. The non-compaction mainly to refuge from predators and, secondly, was fed with of the specimens suggests that the internal part of the ani- the conulariid soft parts. This would be consistent with the mal was filled in at the time of burial, and these remains thesis that carcasses in shallow marine environments provide were introduced inside the central cavity before closing their shelter (Vinn et al. 2018) and would explain the preserva- aperture, e.g. with turbiditic currents. The brachiopod shell tion of the longitudinal bundle remains. The conservation inside of a conulariid (NHMUK PI CL 815, Suppl. material) of these pellets may have been produced through phosphati- probably suffered from predation as has a clear circular drill zation and lithification that allowed them to be preserved hole placed at the level of the brachiopod soft parts, on the three-dimensionally. external part of the theca. This probably represents a unique The British specimens did not show any clear inter- and successful predation attempt. nal structure. One of the specimens has crinoid ossicles There is an individual without bioturbation marks in (Fig. 9) close to the aperture. These ossicles are com- the interior of the theca that has cylindrical pellets run- mon throughout the Much Wenlock Limestone Formation ning underneath and parallel to the theca to form bands (Homerian) of Dudley, in the shallowest water deposits (NHMUK PI CL 801, Suppl. material). The longitudinal represented by crinoidal grainstone beds. These may have 13 Internal conulariid structures unveiled using μCT Fig. 8  Views of the four faces of NHMUK PI CL 601 (seen exter- thal injuries (incomplete scars indicated by white arrows). Paraconu- nally on A, C, E, G) keeping four longitudinal bundles diverted from laria sp. from Finis Shale Member of Texas the apical part (seen internally on B, D, F, H). With lethal and suble- been caught by the living conulariid during a period of composition of calcium phosphate, also with S­ iO2, K-feld- high energy or storm that, with a rapid burial of the speci- spar and Na-feldspar grains up to 40 μm in size. The soft men, allowed its preservation in three dimensions, includ- part remains are mainly represented by ­Fe2O3, and some ing the aperture. minor contribution of Zn. There are also framboidal iron Elemental mapping of the specimen NHMUK PI CL 855, oxide granules which also represent soft remains (Fig. 10). from the Middle Wewoka Member, shows a predominant 13  C. Sendino et al. Most of the individuals that preserve longitudinal bun- dles (45% of the scanned individuals) at the apical part can be seen diverting from this area and extending through the theca. This occurs indistinctly in both North American sites. Ten individuals (30%) show a unique longitudinal structure as a “V” inside the theca cavity (Fig. 7c, e). This structure has both sides with a tubular form of similar size. Four individuals (12%) display a much thicker longitudinal tubular bundle than the rest of the bundles that extends and turns adaperturally (e.g. NHMUK PI CL 602: Fig. 7a) in the same way as Babcock and Feldmann (1986b: Fig. 30.5) illustrated. This structure starts close to the corner adapically and extends in oval-shape adaperturally and centripetally. There is another individual (NHMUK PI CL 855: Fig. 7b) which has only preserved a longitudinal bundle that extends from the apical area to the apertural hinge level. The asym- metric position of this structure prevents us from suggesting it could be the potential gastric cavity. But, could this asym- Fig. 9  Apertural view of NHMUK PI CL 998, with crinoid ossi- metric position be triggered by the death of the organism? cles (in orange) close to the aperture, Paraconularia 'quadrisulcata' McMahon et al. (2017) studied how a sea anemone decays from Much Wenlock Limestone Formation (Homerian), Dudley, in and documented the morphological changes the animal suf- Worcestershire (England) fered. They detailed how the column contracted near the time of death and changed its shape dramatically afterwards. Discussion Moreover, the muscular bundles were the most resistant to degradation. This matches with conulariid soft parts, where The four longitudinal bundles diverting from the apical muscle bundles have been preserved. The dysoxic condi- part that have been observed in one of the specimens tions in which these specimens have been buried would have (NHMUK PI CL 601: Fig. 8, Finis Shale) compare well favoured their preservation. Although McMahon et al.’s with the muscle bundles described in fossil and extant (2017) work could be extrapolated to putative soft-bodied cnidarians. These bundles are arranged in a quadrilateral organisms, conulariids are biomineralized; their thin thecae pattern, diverting dichotomously along the oral-aboral (composed of carbonate-rich apatite) show an alternation of axis. They start at the apical area with a perradial posi- organic poor and organic-rich microlamellae that could not tion and extending adaperturally in a slightly different help with the preservation of soft tissues in the fossil record, position, probably due to contraction after the organism’s with few exceptions such as some of these specimens from death. The fact they can be seen as a layer adaperturally the Pennsylvanian of the North American Midcontinent. relate them to the ectodermal longitudinal and endoder- These longitudinal bundles are interpreted as part of the mal circular muscle layers of the cnidarian column. The muscular system and the oval-shaped structure as the gas- specimen is preserved in three dimensions, like the rest tric cavity. The latter’s preservation in a few individuals may of the individuals studied, due to entrance of sediment have been produced because of altered remains of partially inside the central cavity, probably during a storm episode digested food matter and/or sediment left in its interior when or because of turbidity currents. It may be then when the the animals died. The soft tissues are mainly preserved by muscles closed the aperture. The preservation of these iron minerals which replicate the original shape. Some lon- bundles may have taken place via authigenic replacement gitudinal bundles can be seen partially pyritised (NHMUK of muscular tissues enabled by rapid burial, probably at PI CL 803, Suppl. material). SEM analyses on iron mineral the same place where the individuals lived. In case, they grains with preserved soft tissue show a difference in crystal were exposed after burial, the soft parts would have hardly size and morphology inside the theca. On the other hand, been preserved and the thecae would have bioturbation McMahon et al’s. (2017) work could explain why tentacles structures (Fig. 6a). This could happen when the individu- are hardly preserved in the fossil record and have been only als were transported to more oxygenated waters. In this described to date in putative conulariids. It seems tentacles last case, the thecae would keep their three dimensions are no longer discernible 6 days after the death of cnidarian because cnidarians decay from outside-in, retaining their polyps. three-dimensionality long after all internal characters have Although conulariid muscle bundles have been assumed fully decayed (Hancy and Antcliffe 2020). to have interradial positions, these specimens, from both 13 Internal conulariid structures unveiled using μCT Fig. 10  A Energy-dispersive spectrometry net intensity elemental map mixed with the back-scattered electron image (11,203 × 5968 pixels). Calcium phosphate is represented by phosphorous (green) and the soft tissue by iron (red) oxide. B Detail of the outlined rectangle in A showing framboidal iron oxide in the soft part remains. Silicon (blue) dioxide, sodium (turquoise) feldspar (Nafs) and potassium (magenta) feldpar (Kfs) grains are present within calcium phosphate Graham and Wewoka sites and of two different taxa, have would also explain why there are fewer predation marks predominant perradial positions agreeing with Babcock on the Finis Shale thecae. Furthermore, the thecae are also and Feldmann (1986b). The individual that preserves four better preserved. The only specimen with four “V-shaped” longitudinal muscles keeps three out of the four bundles at longitudinal bundles has been found in Finis Shale deposits. the perirradii (NHMUK PI CL 601, Fig. 8, Suppl. mate- The Wewoka specimens inhabited more shallow waters and rial). There are also specimens with a couple of narrower wave action would certainly be sufficient to break their the- and shorter interradial longitudinal bundles (NHMUK PI cae after the organism’s death. Moreover, Wewoka conulari- CL 602, Suppl. material). Both kind of bundles may extend ids have suffered from transport (Olszewski and West 1997). dichotomously. We cannot forget that the morphology of The fact that those specimens that keep the aperture/oper- these muscle bundles has to be affected by the contraction culum, and this is closed, means the individuals were able at the time of the burial. Those longitudinal structures from to contract their muscular system to close their aperture. the Graham Formation seem to be better preserved, prob- This ability to perform muscle contraction is one of the most ably because of the lower oxygen content as the grey shales important and distinctive features of eumetazoans, holding are darker than the Wewoka ones. More dysoxic conditions important information and informative phylogenetic position 13  C. Sendino et al. for understanding muscle evolution (Leclère and Röttinger to the aperture. Although the hole seems not penetrate deep 2017). Any movement, not only contraction, but also exten- inside the theca, the theca interior cavity is very bioturbated. sion, was regulated by the nervous system. The study of their This drilling hole runs inside at an acute angle. Scalloped muscular system may give new insights into the organisa- and cleft scars can be discerned thanks to the theca orna- tion of a muscle system in a non-bilaterian organism and mentation when this is affected. The fact that Wewoka indi- help with molecular clock studies of cnidarians. The longi- viduals suffered more from predation than the Finis Shale tudinal bundles responsible for closing the aperture seem to ones is reflected in their preservation. Once the thecae have reach the aperture hinge (Fig. 7c–e). Most of the specimens perforations, they are more vulnerable to theca breaks at that keep the aperture do not have soft tissue or longitudinal the weak areas in case of storms; and give less resistance to bundle remains at the apertural area. There is one specimen taphonomic forces before or after burial. Abiotic processes, (NHMUK PI CL 849, Suppl. material) with a fragment of such as pressure solution due to compaction of the sediment longitudinal bundle detached from other area such as a cor- and abrasion, are facilitated. ner. The reason there is no soft tissue at the apertural area It is possible that predation was selective and affected may be due to contraction at the time of the burial (Frickh- young individuals more than adult ones as happens with inger 1994) and the preservation state, probably with sedi- corals (Wood 2003) and also with more predisposition for ment in this area. some taxa than other. If predation more strongly affected Several individuals displaying healed injuries may con- youngsters, this would explain why most of the specimens tribute to understand the distribution of the living soft parts studied, which have predation marks, have very small sizes, as these tissues were affected by predation and covered the of several centimeters long (Fig. 1) with the exception of damaged theca area, displaying incredible plasticity in their a few individuals that do not have clear predation marks. regeneration. The thecae are the canvases where the preda- Probably, the percentage of individuals which reached the tory attacks are recorded. There are other individuals with adulthood was very low due to predation, triggering sig- very damaged thecae that we cannot differentiate if they nificant changes to its population regarding mean size, as are due to predation or postmortem breakage, as the lethal a result of selective removal of small prey by predators. In attacks could destroy the prey, or could be mistaken preda- the case of ‘Conularia crustula’, this species did not sur- tion, in which predators break the thecae of dead organisms vive the Pennsylvanian. This could be due to slow rate of believing they were alive. On the other hand, it is possible growth, considered as disadvantageous to sessile organisms to see that there are individuals with puncture injuries (e.g. (Wood 2003) and their ability to regenerate soft tissue and NHMUK PI CL 604: Fig. 4) which could be non-lethal. theca, both depending on species’ abilities of regeneration, Their soft parts in the theca interior cavity protrude lining concerning lesion size and environmental factors. One of the with the theca. In case of lethal injuries (e.g. NHMUK PI CL Wewoka individuals (NHMUK PI CL 635, Suppl. material) 639: Fig. 11), the puncture injuries do not have soft tissues suffered from predation, with sublethal injuries from which underlying in the theca cavity. The ability to heal injured the animal recovered and healed its theca, but probably not areas coincides with extant coronates (Chapman and Werner completely its soft tissue as seen in the µCT scan (Fig. 12). 1972). Although the specimen is fragmented, there are thicker lon- Most of the North American individuals have very dam- gitudinal bundle remains in other parts of the theca interior aged thecae, due to mechanical damage, produced mainly cavity. Alternately the individual could have been attacked by severe predatory attacks (mostly Wewoka Formation again, being broken by the weakest area and withdrawn part specimens), and by biostratinomic factors (mainly Graham of their soft tissues, or maybe the theca was broken and the Formation specimens) such as bioerosion and dissolution soft tissues were not preserved. typical of muddy offshore environments. Very different is The fact that the individuals lived in relatively shallow the case of the British individuals which have very subtle waters would expose them to more predation than deep repaired thecae, with scalloped scars. These latter could have waters. Bioturbation with scavenging should have occurred been produced as the previous ones by unsuccessful preda- when the specimens were exposed on the bottom and would tion, but also by friction between individuals of the same be responsible, in part, for the lack of soft tissue preserved. or different taxa. The biotic origin of the marks found in On the other hand, there are numerous individuals in both conulariids is distinguished by their geometric shape as hap- Pennsylvanian sites that keep their apertures complete and pens with puncture injuries and their non-random distribu- closed. By analogy with some recent Cnidaria, the conu- tion being preferentially located at the corners. Some thecae lariids could have closed their aperture as a way of defense show multiple scars, after failed attacked and reconstruc- when they felt threatened by predators or any other risk tion of the thecae, and also lethal puncture injuries. Drill- (Werner 1970; Holst and Jarms 2006). It had to be vital for ing millimeter holes related to bioturbation have been seen the conulariid survival to preserve their soft parts. Apart (NHMUK PI CL 851, Wewoka Fm, Suppl. material) close from predation and bioturbation, additional causes of the 13 Internal conulariid structures unveiled using μCT Fig. 11  Individual NHMUK PI CL 639 with puncture injuries, without clear soft tissues underlying in the theca cavity. ‘Conularia crustula’ from Middle Wewoka Member of Oklahoma. External view of each face: (A), (C), (E), and (G). Internal views: (B), (D), (F) and (H) theca incompleteness could be storm breakage, crushing and dysoxic waters in which these conulariids where deposited dissolution while buried (Klompmaker et al. 2019). and more importantly due to the exceptional conditions of Although most of the specimens from the Wewoka the deeper environment in which these organisms would sites have sublethal injury marks, most of them have what lay (Conway Morris 1986). The reason why the soft tis- seems to be remains of soft parts, longitudinal bundles in sues were preserved should have also been because they case of non-lethal injuries. As they have been preserved, were alive at the time of their rapid deposition, in fine this may be due to a low proportion of burrowers in the claystones, and rapid burial (Hagadorn et al. 2002). Some 13  C. Sendino et al. Fig. 12  Individual with severe sublethal injury from which the animal recovered and healed its theca (see discussion). NHMUK PI CL 635, ‘Conularia crustula’ from Middle Wewoka Member of Oklahoma. A External view with scar. B internal view of the soft remains of the individuals suffered storm events or turbidity cur- rents. This is indicated by grain ingestion, possibly sand grains, by the thecae (Fig. 6b). It has been reported that recent coronate polyps locked by grains in more than 80% could survive months (Holst and Jarms 2006). In our case, the specimen is almost 100% filled by grains. Its survival should have been much more reduced. For a good preser- vation, it is also necessary to have had the right conditions for authigenic replacement. Some of the soft tissues have been replaced by pyrite. This is seen in blocky and sub- tle concentrations at the longitudinal bundles, indicating decaying soft tissues. Only 23% of the scanned individuals present bioturbation structures and very subtle longitudi- nal structures. All the studied specimens are preserved in three dimensions, although they are incomplete. Their preservation was facilitated by infilling the theca with mud that later would become a concretion that preserved from crushing during the biostratinomic processes. The pres- ervation of such soft bodies requires low hydrodynamic energy and rapid burial. These are among the best pre- served conulariids known due to their soft tissues being preserved (see reconstruction of the conulariid soft parts seen under CT scan: Fig. 13). Their abundance in the Hughes (Oklahoma) and Jackson (Texas) counties implies they may have been very common in the Pennsylvanian. Possible predators susceptible of predation under low water oxygen levels are some gastropods, cephalopods, arthropods (probably phyllocarids), fishes and sharks. All of these groups have been found associated with conulariids Fig. 13  Reconstruction of the possibly conulariid soft parts seen in both North American sites and could be responsible for under µCT the attacks suffered by the conulariids. Cladodontid sharks 13 Internal conulariid structures unveiled using μCT have already been reported as conulariid crushers in the bundles have predominant perradial positions. The under- Pennsylvanian by Mapes et al. (1989). standing of these structures will help to elucidate the rela- The act that there are some individuals with only a tionship of conulariids in cnidarian phylogeny. V-shaped longitudinal bundle could be explained by pre- dation and preservation. If the individuals which were predated withdrew some of their soft parts, the remains Supplementary Information The online version contains supplemen- tary material available at https://d​ oi.o​ rg/1​ 0.1​ 007/s​ 12542-0​ 23-0​ 0649-7. left would retract as much as they could. When they were able to build a scar, their soft parts would reinforce the theca (NHMUK PI CL 604, Suppl. Material). There are Acknowledgements Thanks to Lucie Goodayle, NHMUK Science a couple of individuals (NHMUK PI CL 603, CL 812, Photographer, for the macro photographs and Oscar Ocaña Vicente, Suppl. material and Fig. 7c, d for CL 812) in which it is Museo del Mar de Ceuta, Ceuta (Spain), for exchanging ideas. We also thank Greg Edgecombe (NHMUK) for advice, Olev Vinn (University possible to see the V-shaped longitudinal bundles with a of Tartu), Mike Reich (Staatliches Naturhistorisches Museum Braun- third bundle partially preserved. All the bundles merge schweig) and an anonymous reviewer for the revision and suggestions. apically. Other specimens keep only intermittent sections of the longitudinal bundles (NHMUK PI CL 611, Suppl. Author Contributions Project designed by CS. Fossil and recent mate- rial prepared by CS, BC, WR and ML. Geological part prepared by material), probably by bioturbation and scavenging. WR. Analyses performed by BC and TS. Written by CS and assessed by Those individuals that we consider to have remains of ACM. Text regarding comparisons to recent specimens written by ACM. the gastric cavity (NHMUK PI CL 602, CL 613, CL 803 and probably CL 855: Fig. 7a, b, Suppl. material) would Funding This research was supported by the Natural History Museum (CS, BD, TS, ML) and had financial support from CNPq have the mouth associated with that cavity and tentacles (309440/2019–0) (ACM). This is a contribution of NP-BioMar USP. would be responsible for the conulariid feeding. These tentacles would be extended during their feeding and could Data availability statement The original contributions presented in this have been formed of different tissues from the mouth. In study are complemented by the Supplementary material. extant coronates, the mouth plate and tentacles are made of the same ectodermal tissue layer, but with different types Declarations of cells depending on the area. On the other hand, the cav- Conflict of interest The authors declare no competing interests. ity occupies the whole internal space, with the endoderm layer lining the theca. Any kind of muscle bundles are Open Access This article is licensed under a Creative Commons Attri- bution 4.0 International License, which permits use, sharing, adapta- inside the cavity as outgrowths of the endodermal tissue tion, distribution and reproduction in any medium or format, as long layer (see Fig. 13 for reconstruction). as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are Conclusions included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not The Pennsylvanian conulariids of the North American permitted by statutory regulation or exceeds the permitted use, you will Midcontinent (Texas and Oklahoma, USA) have been stud- need to obtain permission directly from the copyright holder. To view a ied by µCT scanning and revealed for first time muscular copy of this licence, visit http://​creat​iveco​mmons.​org/​licen​ses/​by/4.​0/. bundles, conulariid soft parts, in three dimensions and a potential gastric cavity. These individuals have been pre- served thanks to the exceptional conditions of the Wewoka and Graham deposits. Most of the Wewoka specimens References have predation scars that have affected the theca and soft parts, and others have lethal injuries. The soft parts have Babcock, L.E., and R.M. Feldmann. 1986a. Devonian and Mississip- pian conulariids of North America. part A. General description been preserved in different ways, some showing the poten- and Conularia. Annals of Carnegie Museum 55: 349–410. tial gastric cavity with muscle bundles and others keeping Babcock, L.E., and R.M. Feldmann. 1986b. Devonian and Mississip- only the muscle bundles. The presumed gastric cavity is pian conulariids of North America. part B. Paraconularia, Reticu- oval-shaped and can be seen fused to a muscle bundle. laconularia, new genus, and organisms rejected from Conulariida. Annals of Carnegie Museum 55: 411–479. The muscle bundles fuse apically or medially, normally Barrande, J. 1855a. Über die Ausfüllung des Siphons gewisser paläo- forming V-shaped pairs, and they extend along the theca, zoischer Cephalopoden auf organischem Wege. Neues Jahrbuch parallel to the corner, towards the aperture. Longitudinal Für Mineralogie, Geologie Und Paläontologie 1855: 385–410. 13  C. Sendino et al. Barrande, J. 1855b. Remplissage organique du siphon dans certains Lobza, V., J. Schieber, and M. Nestell. 1994. The influence of sea level céphalopods paléozoïques. Bulletin de la Société géologique de changes and possible pycnocline shifts on benthic communities in France [2] 12: 441–489. the Finis Shale (Virgilian) near Jacksboro, north-central Texas. Pan- Barrande, J. 1867. Systême silurien du centre de la Bohême, 1 ère. Par- gea; global environments and resources. Memoir, Canadian Society tie: Recherches Paléontologiques, Vol. III. Classe des Mollusques. of Petroleum Geologists 17: 927–947. Ordre des Ptéropodes 3 (1). Prague, Paris: Chez l'auteur et éditeur. Malinky, J.M., and P.H. Heckel. 1998. Paleoecology and taphonomy of Boardman, D R. II, R. H. Mapes, T. E. Yancey and J. M Malinky, J.M. faunal assemblages in gray “Core” (offshore) shales in Midcontinent 1984. A new model for the depth related allogenic community Pennsylvanian Cyclothems. Palaios 13: 311–334. https://​doi.​org/​ succession within North American Pennsylvanian cyclothems 10.​2307/​35153​21. and implications on the black shale problem. In Limestone of Mapes, R.H., T.R. Fahrer, and L.E. Babcock. 1989. Sublethal and lethal the Midcontinent, Spec. Publ. 2, eds. Norman J. Hyne, 141–182. injuries of Pennsylvanian conularids from Oklahoma. Journal of Oklahoma: Tulsa Geological Society Paleontology 63: 34–37. Bouček, B. and F. Ulrich, F. 1929. Étude sur la coquille du genre Conu- McLeod, J.D., M.G. McKinzie, and C. Faulkner. 2003. Cyrtoconic nau- laria Miller. (O skořápce rodu Conularia Miller). Věstník Státního tiloids in the upper Pennsylvanian of North Texas. MAPS Digest geologického ústavu Československé republiky 5, 194–218, pl. 1–2 26: 66–72. Bruthansová, J., and P. Kraft. 2003. Pellets independent of or associated McMahon, S., L.G. Tarhan, and D.E.G. Briggs. 2017. Decay of the sea with Bohemian Ordovician body fossils. Acta Palaeontologica anemone Metridium (Actiniaria): implications for the preservation Polonica 48: 437–445. of cnidarian polyps and other soft-bodied diploblast-grade animals. Chapman, D.M., and B. Werner. 1972. Structure of a solitary and a Palaios 32: 388–395. https://​doi.​org/​10.​2110/​palo.​2016.​102. colonial species of Stephanoscyphus (Scyphozoa, Coronatae) with Miller, A.A., S.M. Jacquet, E.P. Anderson, and J.D. Schiffbauer. 2022. observations on periderm repair. Helgoländer Wissenschaftliche Conulariids from the Silurian (late Telychian) Waukesha Lager- Meeresuntersuchungen 23: 393–421. https://​doi.​org/​10.​1007/​BF016​ stätte, Wisconsin. Historical Biology. https://​doi.​org/​10.​1080/​08912​ 25293. 963.​2021.​20179​17. Conway Morris, S. 1986. The community structure of the middle Cam- Moore, R.C., and H.J. Harrington. 1956. Scyphozoa. In Treatise on brian phyllopod bed (Burgess Shale). Palaeontology 29: 423–467. invertebrate Paleontology, coelenterata, F, ed. Raymond C. Moore, Demaison, G.J., and G.T. Moore. 1980. Anoxic environments and oil F27–F38. New York, Lawrence and Boulder: Geological Society of source bed genesis. American Association of Petroleum Geologists, America and University of Kansas Press. Bulletin 64: 1179–1209. https://​doi.​org/​10.​1016/​0146-​6380(80)​ Morandini, A.C., and G. Jarms. 2010. Identification of the coronate polyp 90017-0. from the Arctic Ocean: Nausithoe werneri Jarms, 1990 (Cnidaria, Scy- Frickhinger, K.A. 1994. Die Fossilien von Solnhofen. Korb: phozoa, Coronatae), with notes on the biology. Steenstrupia 32: 69–77. Goldschneck-Verlag. Olszewski, T.D., and R.R. West. 1997. Influence of transportation and Hagadorn, J.W., R.H. Dott Jr., and D. Damrow. 2002. Stranded on a late time-averaging in fossil assemblages from the Pennsylvanian of Cambrian shoreline: medusae from central Wisconsin. Geology 30: Oklahoma. Lethaia 30: 315–329. https://​doi.​org/​10.​1111/j.​1502-​ 147–150. https://​doi.​org/​10.​1130/​0091-​7613(2002)​030%​3c0147:​ 3931.​1997.​tb004​75.x. SOALCS%​3e2.0.​CO;2. Plummer, F.B. 1919. Preliminary paper on the stratigraphy of the Penn- Hancy, A.D., and J.B. Antcliffe. 2020. Anoxia can increase the rate of sylvanian formations of North-Central Texas. Bulletin of the Ameri- decay for cnidarian tissue: using actinia equina to understand the can Association of Petroleum Geologists 3: 132–150. https://​doi.​org/​ early fossil record. Geobiology 18: 167–184. https://​doi.​org/​10.​1111/​ 10.​1306/​3D932​514-​16B1-​11D7-​86450​00102​C1865D. gbi.​12370. Sendino, C., and M.M. Bochmann. 2021. An exceptionally pre- Heckel, P.H. 1991. Thin widespread Pennsylvanian black shales of Mid- served conulariid from Ordovician erratics of Northern Euro- continent North America: a record of a cyclic succession of wide- pean Lowlands. PalZ 95: 71–84. https:// ​ d oi. ​ o rg/ ​ 1 0. ​ 1 007/​ spread pycnoclines in a fluctuating epeiric sea. Geological Society s12542-​020-​00534-7. Special Publication 58: 259–273. https://​doi.​org/​10.​1144/​GSL.​SP.​ Steul, H. 1984. Die systematische Stellung der Conularien. Giessener 1991.​058.​01.​17. Geologische Schriften 37: 1–117. Hergarten, B. 1994. Conularien des Hunsrückschiefers (Unter-Devon). Ure, D. 1793. The History of Rutherglen and East-Kilbride. Glasgow: Senckenbergiana Lethaea 74: 273–290. David Niven. Holst, S., and G. Jarms. 2006. Responses of solitary and colonial coro- Van Iten, H., and W.H. Südkamp. 2010. Exceptionally preserved conu- nate polyps (Cnidaria, Scyphozoa, Coronatae) to sedimentation and lariids and an edrioasteroid from the Hunsrück Slate (Lower Devo- burial. Journal of Experimental Marine Biology and Ecology 329: nian, SW Germany). Palaeontology 53: 403–414. https://​doi.​org/​10.​ 230–238. https://​doi.​org/​10.​1016/j.​jembe.​2005.​09.​014. 1111/j.​1475-​4983.​2010.​00942.x. Kiderlen, H. 1937. Die conularien. Über Bau und leben der ersten scypho- Vinn, O., A. Ernst, U. Toom, and M. Isakar. 2018. Cryptic encrusting zoa. Neues Jahrbuch Für Mineralogie, Geologie Und Paläontologie, fauna inside invertebrate fossils from the Ordovician of Estonia. Beilage-Band (b: Geologie, Paläontologie) 77: 113–169. Annales Societatis Geologorum Poloniae 88: 285–290. https://​doi.​ Klompmaker, A.A., P.H. Kelley, D. Chattopadhyay, J.C. Clements, J.W. org/​10.​14241/​asgp.​2018.​008. Huntley, and M. Kowalewski. 2019. Predation in the marine fossil Weaver, O.D. 1954. Geology and mineral resources of Hughes County, record: Studies, data, recognition, environmental factors, and behav- Oklahoma. Oklahoma Geological Survey Bulletin 70: 1–150. ior. Earth-Science Reviews 194: 472–520. https://​doi.​org/​10.​1016/j.​ Werner, B. 1966. Stephanoscyphus (Scyphozoa Coronatae) und seine earsc​irev.​2019.​02.​020. direkte Abstammung von den fossilen Conulata. Helgoländer Wis- Kocurko, M.J. 1993. Non-fusulinid foraminifera of the upper Pennsyl- senschaftliche Meeresuntersuchungen 13: 317–347. vanian finis shale, including the description of an enigmatic taxon. Werner, B. 1967. Stephanoscyphus Allman (Scyphozoa Coronatae), ein Tulane Studies in Geology and Paleontology 26: 27–33. rezenter Vertreter der Conulata? Paläontologische Zeitschrift 41: Leclère, L., and E. Röttinger. 2017. Diversity of cnidarian muscles: Function, 137–153. anatomy, development and regeneration. Frontiers in Cell and Devel- opmental Biology 4: 157. https://​doi.​org/​10.​3389/​fcell.​2016.​00157. 13 Internal conulariid structures unveiled using μCT Werner, B. 1970. Weitere Untersuchungen über die Entwicklungsge- White, C. A. 1880. Contributions to invertebrate paleontology no 8: fos- schichte von Stephanoscyphus (Scyphozoa, Coronatae) und seine sils from the carboniferous rocks of the interior States. In United Bedeutung für die evolution der Scyphozoa. Zoologischer Anzeiger, States geological and geographical survey of the territories: a Supplement 33: 159–165. report of progress of the exploration in wyoming and idaho for the Werner, B. 1971. Neue Beitraege zur Evolution der Scyphozoa und year 1878. 12th Ann. Rept., vol. 1, part 1, ed. Ferdinand V. Hayden, Cnidaria. In I Simposio Internacional de Zoofilogenia, ed. Rafael 155–171. Washington: Government Printing Office. Alvarado, Enrique Gadea, and Andrés De Haro, 223–244. Sala- Wood, R. 2003. Predation in ancient reef-builders. In Predator-prey manca: Universidad de Salamanca. interactions in the fossil record, topics in geobiology, ed. Patricia West, R.R. 1970. Marine communities of a portion of the Wewoka Foma- H. Kelley, Michal Kowalewski, and Thor A. Hansen, 33–53. New tion (Pennsylvanian) in Hughes County, Oklahoma. Norman: The York, Boston, Dordrecht, London, Moscow: Kluwer Academic/ University of Oklahoma. Plenum Publishers. 13