Ornithopoda

We present a new dinosaur footprint from Praia do Guincho, Portugal. Praia do Guincho is a seaside locality, situated 2 km north of Cabo Espichel. A loose cast of a tridactyl dinosaur footprint was discovered during fieldwork in 2011. The cliff where the footprint was found is composed of limestones, marls, sandstones and conglomerates that were deposited in shallow marine, lagoon and estuarine environments. The succession belongs to the Papo-Seco Formation (Lower Cretaceous-Barremian). The remains of several groups of vertebrates, including dinosaurs, have been reported in this formation. This paper provides a trackmaker study consisting of a visual analysis under different light angles and photogrammetric 3D modelling. The specimen has a digit III longer than II and IV. However, a substantial part of the shape of digit III is sediment, giving a flawed impression that it belongs to the footprint itself. The photogrammetric modelling revealed that digit III is shorter and more rounded than it appeared to be in the first place and the morphology of the cast (large plantar surface, similar length and width rounded heel, with elongate, narrow digits) matches with the features of the pes of ornithopods and with the characteristics described as belonging to ornithopod dinosaurs. RIASSUNTO-[Nuova scoperta di una impronta di probabile Ornitopode del Cretaceo Inferiore di Cabo Espichel (Sesimbra, Portogallo)]-In questo articolo viene descritta una nuova impronta di dinosauro proveniente da Praia do Guincho, una località marina situata circa a 2 Km a nord di Cabo Espichel. Durante la campagna del 2011, è stato scoperto un calco naturale isolato di un'impronta tridattila di dinosauro. La falesia dove è stata trovata l'impronta è composta da calcari, marne, sabbie e conglomerati, depositatisi in ambiente marino poco profondo, estuarino e lagunare. La successione appartiene alla Formazione di Papo-Seco (Cretaceo Inferiore-Barremiano). In questa formazione sono stati segnalati i resti di vari gruppi di vertebrati, inclusi dinosauri. Questo articolo mira ad identificare l'autore della traccia attraverso lo studio visuale (secondo differenti angoli di illuminazione) e la modellazione fotogrammetrica 3D. Infatti, una parte sostanziale del dito III è composta da sedimento, dando la falsa impressione di appartenere all'impronta stessa. Il dito III sembra pertanto più lungo delle dita II e IV, ma la modellazione fotogrammetrica ha dimostrato come il dito III sia più corto ed arrotondato di quanto appaia. La morfologia dell'impronta (grande superficie plantare, tallone arrotondato con lunghezza e larghezza simili, con le dita allungate e strette) corrisponde alle caratteristiche delle zampe dei dinosauri ornitopodi. Sulla base di confronti morfometrici, riteniamo quindi che l'impronta sia stata prodotta da un ornitopode.

Jaw mechanics in ornithischian dinosaurs have been widely studied for well over a century. Most of these studies, however, use only one or few taxa within a given ornithischian clade as a model for feeding mechanics across the entire clade. In this study, mandibular mechanical advantages among 52 ornithischian genera spanning all subclades are calculated using 2D lever arm methods. These lever arm calculations estimate the effect of jaw shape and difference in adductor muscle line of action on relative bite forces along the jaw. Results show major instances of overlap between taxa in tooth positions at which there was highest mechanical advantage. A relatively low bite force is seen across the tooth row among thyreophorans (e.g., stegosaurs and ankylosaurs), with variation among taxa. A convergent transition occurs from a more evenly distributed bite force along the jaw in basal ornithopods and basal marginocephalians to a strong distal bite force in hadrosaurids and cera-topsids, respectively. Accordingly, adductor muscle vector angles show repeated trends from a mid-range caudodorsal orientation in basal orni-thischians to a decrease in vector angles indicating more caudally oriented jaw movements in derived taxa (e.g., derived thyreophorans, basal ornithopods, lambeosaurines, pachycephalosaurs, and derived ceratop-sids). Analyses of hypothetical jaw morphologies were also performed, indicating that both the coronoid process and lowered jaw joint increase moment arm length therefore increasing mechanical advantage of the jaw apparatus. Adaptive trends in craniomandibular anatomy show that orni-thischians evolved more complex feeding apparatuses within different clades as well as morphological convergences between clades. Anat Rec, 299:271–294, 2016. V C 2015 Wiley Periodicals, Inc.

Several sandstone casts of dinosaur footprints, identified as the ichnogenus Caririchnium, have been recovered from the lower part of the Fossil Forest Member, Fruitland Formation, San Juan Basin, New Mexico. The footprints, which were made by a large hadrosaur, are tridactyl, have broad, rounded heel imprints, and thick toes that terminate in short, narrow claw tips with the largest specimens as much as 940 mm long. Skeletal remains of large hadrosaurs are also known from the Fruitland Formation, so these dinosaurs are now known by both bones and footprints. A reconsideration of the ichnotaxonomy of large ornithopod footprints suggests that only two ichnogenera may be valid: Caririchnium (= Hadrosauropodus) and Amblydactylus (= Iguanodontipus).

During the latest Cretaceous, the European Archipelago was characterized by highly fragmented landmasses hosting putative dwarfed, insular dinosaurs, claimed as fossil evidence of the “island rule”. The Villaggio del Pescatore quarry (north-eastern Italy) stands as the most informative locality within the palaeo-Mediterranean region and represents the first, multi-individual Konservat-Lagerstätte type dinosaur-bearing locality in Italy. The site is here critically re-evaluated as early Campanian in age, thus preceding the final fragmentation stages of the European Archipelago, including all other European localities preserving hypothesized dwarfed taxa. New skeletal remains allowed osteohistological analyses on the hadrosauroid Tethyshadros insularis indicating subadult features in the type specimen whereas a second, herein newly described, larger individual is likely somatically mature. A phylogenetic comparative framework places the body-size of T. insularis in range with other non-hadrosaurid Eurasian hadrosauroids, rejecting any significant evolutionary trend towards miniaturisation in this clade, confuting its ‘pygmy’ status, and providing unmatched data to infer environmentally-driven body-size trends in Mesozoic dinosaurs.