[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

[dinosaur] Oldest crocodylomorph eggs + Triassic tetrapod burrows + whale-crocodilian skull convergence

Ben Creisler

Some recent non-dino papers:

Free pdf:

João Russo , Octávio Mateus, Marco Marzola & Ausenda Balbino (2017) 
Two new ootaxa from the late Jurassic: The oldest record of crocodylomorph eggs, from the Lourinhã Formation, Portugal. 
PLoS ONE 12(3): e0171919. 

The Late Jurassic Lourinhã Formation is known for its abundant remains of dinosaurs, crocodylomorphs and other vertebrates. Among this record are nine localities that have produced either dinosaur embryos, eggs or eggshell fragments. Herein, we describe and identify the first crocodiloid morphotype eggs and eggshells from the Lourinhã Formation, from five occurrences. One clutch from Cambelas, composed of 13 eggs, eggshell fragments from Casal da Rola and Peralta, one crushed egg and eggshells from Paimogo North, and four crushed eggs as well as eggshell fragments from Paimogo South. We observed and confirmed diagnostic morphological characters for crocodiloid eggshells and which are consistent with a crocodylomorph affinity, such as the ellipsoidal shape, wedge-shaped shell units, triangular extinction under cross-polarized light, and tabular ultrastructure. This material is distinctive enough to propose two new ootaxa within the oofamily Krokolithidae, Suchoolithus portucalensis, oogen. and oosp. nov., for the material from Cambelas, the most complete clutch known for crocodiloid eggs, and Krokolithes dinophilus, oosp. nov., for the remaining material. These are the oldest crocodylomorph eggs known, extending the fossil record for this group to the Late Jurassic. Furthermore, except for the clutch from Cambelas, the material was found with theropod eggs and nests, in the other four occurrences, which seem to suggest some form of biological relationship, still unclear at this point.

News: (in Portuguese)




William D. Krummeck & Emese M. Bordy (2017)
Reniformichnus katikatii (New Ichnogenus and Ichnospecies): Continental Vertebrate Burrows from the Lower Triassic, Main Karoo Basin, South Africa.
Ichnos (advance online publication)
doi:  http://dx.doi.org/10.1080/10420940.2017.1292909   

The formal ichnotaxonomic assignment of a new ichnogenus and ichnospecies, Reniformichnus katikatii, is presented based on the holotype and several field specimens from the Lower Triassic Katberg Formation in the main Karoo Basin of South Africa. The holotype is an inclined, burrow cast with bilobate base and reniform cross-section. Its width ranges from 12.6 to 14.7 cm, and its height is 5 to 7.4 cm resulting in an aspect ratio of 1.89 to 2.74. The surface preserves 70–180 mm long ridges running parallel to the long axis of the burrow on the upper parts of the walls and lower parts of the dorsum and shorter ridges (average length ~27 mm) are preserved on the more ventral areas in two opposite orientations, cross-cutting each other in a rhomboid pattern. Burrow fills are passive and consist of slightly bedded, laminated, or massive clastic rocks that are coarser than the host mudstones. The burrow casts are isolated, never occurring in clusters. This simple burrow shows no evidence for branching, spiralling, interconnected tunnels, burrow linings, terminal chambers, or entrances. Preserved in fluvial floodplain mudstone units, the burrows were passively filled by layered, laminated, or massive sand and other coarser clastic sediments. The burrow casts are morphologically similar to unnamed Antarctic ichnotaxa that have been attributed to tetrapods (e.g., therapsids, procolophonids), extending the geographic range of the potential producers of Reniformichnus isp. to continental settings in southern Gondwana. Biostratigraphic evidence on the temporal distribution of Reniformichnus isp. suggests that the trace maker emerged in the aftermath of the Permo-Triassic mass extinction event to successfully burrow throughout the Early Triassic.


Clausen & Colin R. McHenry (2017)
The remarkable convergence of skull shape in crocodilians and toothed whales.
Proceedings of the Royal Society B 2017 284: 20162348
DOI: 10.1098/rspb.2016.2348

The striking resemblance of long-snouted aquatic mammals and reptiles has long been considered an example of morphological convergence, yet the true cause of this similarity remains untested. We addressed this deficit through three-dimensional morphometric analysis of the full diversity of crocodilian and toothed whale (Odontoceti) skull shapes. Our focus on biomechanically important aspects of shape allowed us to overcome difficulties involved in comparing mammals and reptiles, which have fundamental differences in the number and position of skull bones. We examined whether diet, habitat and prey size correlated with skull shape using phylogenetically informed statistical procedures. Crocodilians and toothed whales have a similar range of skull shapes, varying from extremely short and broad to extremely elongate. This spectrum of shapes represented more of the total variation in our dataset than between phylogenetic groups. The most elongate species (river dolphins and gharials) are extremely convergent in skull shape, clustering outside of the range of the other taxa. Our results suggest the remarkable convergence between long-snouted river dolphins and gharials is driven by diet rather than physical factors intrinsic to riverine environments. Despite diverging approximately 288 million years ago, crocodilians and odontocetes have evolved a remarkably similar morphological solution to feeding on similar prey.