Rare evidence for 'gnawing-like' behavior in a small-bodied theropod dinosaur.
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ABSTRACT:
SUBMITTER: Brown CM
PROVIDER: S-EPMC8234920 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:BackgroundHeterodontosaurids are an important but enigmatic and poorly understood early radiation of ornithischian dinosaurs. The late-surviving heterodontosaurid Fruitadens haagarorum from the Late Jurassic (early Tithonian) Morrison Formation of the western USA is represented by remains of several small (<1 metre total body length, <1 kg body mass) individuals that include well-preserved but incomplete cranial and postcranial material. Fruitadens is hypothesized to represent one of the smallest known ornithischian dinosaurs.Methodology/principal findingsWe describe the cranial and postcranial anatomy of Fruitadens in detail, providing comparisons to all other known heterodontosaurid taxa. High resolution micro-CT data provides new insights into tooth replacement and the internal anatomy of the tooth-bearing bones. Moreover, we provide a preliminary functional analysis of the skull of late-surviving heterodontosaurids, discuss the implications of Fruitadens for current understanding of heterodontosaurid monophyly, and briefly review the evolution and biogeography of heterodontosaurids.Conclusions/significanceThe validity of Fruitadens is supported by multiple unique characters of the dentition and hindlimb as well as a distinct character combination. Fruitadens shares highly distinctive appendicular characters with other heterodontosaurids, strengthening monophyly of the clade on the basis of the postcranium. Mandibular morphology and muscle moment arms suggest that the jaws of late-surviving heterodontosaurids, including Fruitadens, were adapted for rapid biting at large gape angles, contrasting with the jaws of the stratigraphically older Heterodontosaurus, which were better suited for strong jaw adduction at small gapes. The lack of wear facets and plesiomorphic dentition suggest that Fruitadens used orthal jaw movements and employed simple puncture-crushing to process food. In combination with its small body size, these results suggest that Fruitadens was an ecological generalist, consuming select plant material and possibly insects or other invertebrates.
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Project description:Islands are noted for the occurrence of aberrant, endemic, and dwarfed taxa (the "island effect"). Late Cretaceous vertebrate assemblages of Romania and elsewhere in Europe are classic examples of island faunas in the fossil record, and are characterized by dwarfed herbivorous dinosaurs and other endemic taxa that are noticeably primitive relative to their mainland contemporaries. Fossils of the predators inhabiting the European paleoislands, however, are exceptionally rare and fragmentary. We describe a new dromaeosaurid theropod, based on an articulated skeleton from the Maastrichtian of Romania, which represents the most complete predatory dinosaur from the middle to Late Cretaceous of Europe. This taxon is characterized by a peculiar body plan, most notably extensive fusion in the hand and distal hindlimb, a highly retroverted pelvis with enlarged femoral muscle attachments, and a pair of hyperextensive pedal claws. However, unlike the island-dwelling herbivorous dinosaurs, its closest relatives are contemporary similar-sized Laurasian taxa, indicating faunal connections between Asia and the European islands late into the Cretaceous. This theropod provides support for the aberrant nature of the Late Cretaceous European island-dwelling dinosaurs, but indicates that predators on these islands were not necessarily small, geographically endemic, or primitive.
| S-EPMC2932599 | biostudies-literature
Project description:BackgroundThe Yellow Cat Member of the Cedar Mountain Formation (Early Cretaceous, Barremian?) of Utah has yielded a rich dinosaur fauna, including the basal therizinosauroid theropod Falcarius utahensis at its base. Recent excavation uncovered a new possible therizinosauroid taxon from a higher stratigraphic level in the Cedar Mountain Formation than F. utahensis.Methodology/principal findingsHere we describe a fragmentary skeleton of the new theropod and perform a phylogenetic analysis to determine its phylogenetic position. The skeleton includes fragments of vertebrae, a scapula, forelimb and hindlimb bones, and an ischium. It also includes several well-preserved manual unguals. Manual and pedal morphology show that the specimen is distinct from other theropods from the Cedar Mountain Formation and from previously described therizinosauroids. It is here named as the holotype of a new genus and species, Martharaptor greenriverensis. Phylogenetic analysis places M. greenriverensis within Therizinosauroidea as the sister taxon to Alxasaurus + Therizinosauridae, although support for this placement is weak.Conclusions/significanceThe new specimen adds to the known dinosaurian fauna of the Yellow Cat Member of the Cedar Mountain Formation. If the phylogenetic placement is correct, it also adds to the known diversity of Therizinosauroidea.
| S-EPMC3430620 | biostudies-literature