An unusual occurrence of a colony of microcrinoids from shale within a fragment of a large orthoc... more An unusual occurrence of a colony of microcrinoids from shale within a fragment of a large orthoconic nautiloid body chamber is described from the Imo Formation (Mississippian, Chesterian) near Elba, Arkansas. The colony, about 70 individuals, consists principally of immature specimens that lack facets for the arms, and a few mature specimens with four or five arm facets. The crinoids are interpreted as record of a census population that was engulfed suddenly by mud. The crinoids are assigned to Allagecrinus coronarius Gutschick, 1968. The body chamber may have been broken during predation by other large cephalopods, or sharks, known from the Imo, or by post-mortem transport. The shell served as a firm substrate on which the microcrinoid larvae could settle and the convex sides may have provided some protection from currents.
Coleoidea (squids and octopuses) comprise all crown group cephalopods except the Nautilida. Coleo... more Coleoidea (squids and octopuses) comprise all crown group cephalopods except the Nautilida. Coleoids are characterized by internal shell (endocochleate), ink sac and arm hooks, while nautilids lack an ink sac, arm hooks, suckers, and have an external conch (ectocochleate). Differentiating between straight conical conchs (orthocones) of Palaeozoic Coleoidea and other ectocochleates is only possible when rostrum (shell covering the chambered phragmocone) and body chamber are preserved. Here, we provide information on how this internalization might have evolved. We re-examined one of the oldest coleoids, Gordoniconus beargulchensis from the Early Carboniferous of the Bear Gulch Fossil-Lagerstätte (Montana) by synchrotron, various lights and Reflectance Transformation Imaging (RTI). This revealed previously unappreciated anatomical details, on which we base evolutionary scenarios of how the internalization and other evolutionary steps in early coleoid evolution proceeded. We suggest tha...
FIG. 8. — Surface rendering generated from CT Scan slices of AMNH FF 20852: A, postero-lateral vi... more FIG. 8. — Surface rendering generated from CT Scan slices of AMNH FF 20852: A, postero-lateral view of the braincase (blue); the transverse microtomographic slices of B and C are indicated in red line. The red colored area of the braincase in B and C represent the intramural diverticuli of the posterior fossa bridgei. Abbreviations: see Material and methods. Scale bars: 5 mm.
FIG. 3. — Surface rendering generated from CT Scan slices of the dorsal surface of the braincase ... more FIG. 3. — Surface rendering generated from CT Scan slices of the dorsal surface of the braincase (blue) of AMNH FF 20852. Grey area, not perichondrally lined surface. Abbreviations: see Material and methods. Scale bar: 5 mm.
FIG. 7. — Surface rendering generated from CT Scan slices of AMNH FF 20852 in posterior view: A, ... more FIG. 7. — Surface rendering generated from CT Scan slices of AMNH FF 20852 in posterior view: A, braincase (blue); B, braincase and associated bones (intercalar in pink; parasphenoid in red). Grey area, not perichondrally lined surface. Abbreviations: see Material and methods. Scale bar: 5 mm.
FIG. 9. — Microtomographic slices through the intercalars of AMNH FF 20852: A, cross section; B, ... more FIG. 9. — Microtomographic slices through the intercalars of AMNH FF 20852: A, cross section; B, saggital section through the left intercalar. Abbreviations: see Material and methods. Scale bar: 5 mm.
Recovery of hyoliths from the Eudora Shale in southeastern Kansas and the Wolf Mountain Shale in ... more Recovery of hyoliths from the Eudora Shale in southeastern Kansas and the Wolf Mountain Shale in north-central Texas constitutes the first occurrences of this group from the Pennsylvanian of North America. All specimens are preserved as pyritized internal molds. Many are sufficiently well preserved to be distinguishable from Hyolithes on the basis of transverse section and internal ornamentation; these are referred to Lirotheca wilsoni n. gen., n. sp. All other specimens lacking ornament and other distinctive features are assigned to Hyolithes? sp. The Kansas hyoliths occur with an abundant and diverse fauna including juvenile ammonoids and other molluscs, many of which are less than 3 mm in length. This suggests that these molluscs including the hyoliths are juvenile. The Texas hyoliths occur with a normal-size marine fauna, but their degree of maturity cannot be determined readily because they are too fragmentary.--Journal abstract.
Reinterpretation of the North American Strobilepis spinigera Clarke 1888 from the Devonian and th... more Reinterpretation of the North American Strobilepis spinigera Clarke 1888 from the Devonian and the find of Diadeloplax paragrapsima gen. et sp. n. from the Pennsylvanian provide the basis for the recognition of a new class of uncertain affinity, Multiplacophora. The range of the class is Middle Devonian (Erian) to Pennsylvanian (Morrowan). Multiplacophora differ from the order Hercolepadida and the classes Tharnbetolepida and Polyplacophora in the number, shape, and arrangement of plates; the presence of large spines; and the complexity of internal canal systems in the plates and spines.
Three new species of Hippocardia, H. ancora, H. pala, and H. cucullata, are described. Hippocardi... more Three new species of Hippocardia, H. ancora, H. pala, and H. cucullata, are described. Hippocardia ancora and H. pala occur together in the Lazy Bend Formation (Desmoinesian) of Texas. Hippocardia cucullata occurs in the Imo Formation (Chesterian) of Arkansas.
Damage displayed by 18 of 954 relatively mature (> 35 mm diameter) specimens ofGonioloboceras ... more Damage displayed by 18 of 954 relatively mature (> 35 mm diameter) specimens ofGonioloboceras goniolobum(Meek) from North American Midcontinent Upper Carboniferous sediments is interpreted to be bite marks caused by condrichthyans and other fish, particularly the symmoriid sharkSymmorium reniforme.It is likely that these and other predators regularly preyed onGonioloboceras goniolobumbecause all of the analyzed specimens ofGoniolobocerasexhibit some evidence of unrepaired damage, including broached camerae and missing body chambers. Two new characteristics utilized with caution to detect predatory events on ammonoids are raised oval or circular pedestals on internal molds and the breakage and termination of septa in conjunction with a broken external shell. When sufficient damage to theGoniolobocerasconchs occurred during predatory attacks, the broached camerae flooded, the conch became negatively buoyant, and it sank in the vicinity of the attack. When preserved, these conchs fo...
An unusual occurrence of a colony of microcrinoids from shale within a fragment of a large orthoc... more An unusual occurrence of a colony of microcrinoids from shale within a fragment of a large orthoconic nautiloid body chamber is described from the Imo Formation (Mississippian, Chesterian) near Elba, Arkansas. The colony, about 70 individuals, consists principally of immature specimens that lack facets for the arms, and a few mature specimens with four or five arm facets. The crinoids are interpreted as record of a census population that was engulfed suddenly by mud. The crinoids are assigned to Allagecrinus coronarius Gutschick, 1968. The body chamber may have been broken during predation by other large cephalopods, or sharks, known from the Imo, or by post-mortem transport. The shell served as a firm substrate on which the microcrinoid larvae could settle and the convex sides may have provided some protection from currents.
Coleoidea (squids and octopuses) comprise all crown group cephalopods except the Nautilida. Coleo... more Coleoidea (squids and octopuses) comprise all crown group cephalopods except the Nautilida. Coleoids are characterized by internal shell (endocochleate), ink sac and arm hooks, while nautilids lack an ink sac, arm hooks, suckers, and have an external conch (ectocochleate). Differentiating between straight conical conchs (orthocones) of Palaeozoic Coleoidea and other ectocochleates is only possible when rostrum (shell covering the chambered phragmocone) and body chamber are preserved. Here, we provide information on how this internalization might have evolved. We re-examined one of the oldest coleoids, Gordoniconus beargulchensis from the Early Carboniferous of the Bear Gulch Fossil-Lagerstätte (Montana) by synchrotron, various lights and Reflectance Transformation Imaging (RTI). This revealed previously unappreciated anatomical details, on which we base evolutionary scenarios of how the internalization and other evolutionary steps in early coleoid evolution proceeded. We suggest tha...
FIG. 8. — Surface rendering generated from CT Scan slices of AMNH FF 20852: A, postero-lateral vi... more FIG. 8. — Surface rendering generated from CT Scan slices of AMNH FF 20852: A, postero-lateral view of the braincase (blue); the transverse microtomographic slices of B and C are indicated in red line. The red colored area of the braincase in B and C represent the intramural diverticuli of the posterior fossa bridgei. Abbreviations: see Material and methods. Scale bars: 5 mm.
FIG. 3. — Surface rendering generated from CT Scan slices of the dorsal surface of the braincase ... more FIG. 3. — Surface rendering generated from CT Scan slices of the dorsal surface of the braincase (blue) of AMNH FF 20852. Grey area, not perichondrally lined surface. Abbreviations: see Material and methods. Scale bar: 5 mm.
FIG. 7. — Surface rendering generated from CT Scan slices of AMNH FF 20852 in posterior view: A, ... more FIG. 7. — Surface rendering generated from CT Scan slices of AMNH FF 20852 in posterior view: A, braincase (blue); B, braincase and associated bones (intercalar in pink; parasphenoid in red). Grey area, not perichondrally lined surface. Abbreviations: see Material and methods. Scale bar: 5 mm.
FIG. 9. — Microtomographic slices through the intercalars of AMNH FF 20852: A, cross section; B, ... more FIG. 9. — Microtomographic slices through the intercalars of AMNH FF 20852: A, cross section; B, saggital section through the left intercalar. Abbreviations: see Material and methods. Scale bar: 5 mm.
Recovery of hyoliths from the Eudora Shale in southeastern Kansas and the Wolf Mountain Shale in ... more Recovery of hyoliths from the Eudora Shale in southeastern Kansas and the Wolf Mountain Shale in north-central Texas constitutes the first occurrences of this group from the Pennsylvanian of North America. All specimens are preserved as pyritized internal molds. Many are sufficiently well preserved to be distinguishable from Hyolithes on the basis of transverse section and internal ornamentation; these are referred to Lirotheca wilsoni n. gen., n. sp. All other specimens lacking ornament and other distinctive features are assigned to Hyolithes? sp. The Kansas hyoliths occur with an abundant and diverse fauna including juvenile ammonoids and other molluscs, many of which are less than 3 mm in length. This suggests that these molluscs including the hyoliths are juvenile. The Texas hyoliths occur with a normal-size marine fauna, but their degree of maturity cannot be determined readily because they are too fragmentary.--Journal abstract.
Reinterpretation of the North American Strobilepis spinigera Clarke 1888 from the Devonian and th... more Reinterpretation of the North American Strobilepis spinigera Clarke 1888 from the Devonian and the find of Diadeloplax paragrapsima gen. et sp. n. from the Pennsylvanian provide the basis for the recognition of a new class of uncertain affinity, Multiplacophora. The range of the class is Middle Devonian (Erian) to Pennsylvanian (Morrowan). Multiplacophora differ from the order Hercolepadida and the classes Tharnbetolepida and Polyplacophora in the number, shape, and arrangement of plates; the presence of large spines; and the complexity of internal canal systems in the plates and spines.
Three new species of Hippocardia, H. ancora, H. pala, and H. cucullata, are described. Hippocardi... more Three new species of Hippocardia, H. ancora, H. pala, and H. cucullata, are described. Hippocardia ancora and H. pala occur together in the Lazy Bend Formation (Desmoinesian) of Texas. Hippocardia cucullata occurs in the Imo Formation (Chesterian) of Arkansas.
Damage displayed by 18 of 954 relatively mature (> 35 mm diameter) specimens ofGonioloboceras ... more Damage displayed by 18 of 954 relatively mature (> 35 mm diameter) specimens ofGonioloboceras goniolobum(Meek) from North American Midcontinent Upper Carboniferous sediments is interpreted to be bite marks caused by condrichthyans and other fish, particularly the symmoriid sharkSymmorium reniforme.It is likely that these and other predators regularly preyed onGonioloboceras goniolobumbecause all of the analyzed specimens ofGoniolobocerasexhibit some evidence of unrepaired damage, including broached camerae and missing body chambers. Two new characteristics utilized with caution to detect predatory events on ammonoids are raised oval or circular pedestals on internal molds and the breakage and termination of septa in conjunction with a broken external shell. When sufficient damage to theGoniolobocerasconchs occurred during predatory attacks, the broached camerae flooded, the conch became negatively buoyant, and it sank in the vicinity of the attack. When preserved, these conchs fo...
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