bioRxiv Science⌕ Search
Home/Archive/bioRxiv

bioRxiv · 10.1101/2022.09.20.508522

Femora from an exceptionally large population of coeval ornithomimosaurs yield evidence of sexual dimorphism in extinct theropod dinosaurs

Pintore, R.·Cornette, R.·Houssaye, A.·Allain, R.
View original source ↗Export metadata ↓

Abstract

Sexual dimorphism is challenging to detect among fossils, due to a lack of statistical representativeness. The Angeac-Charente Lagerstatte (France) represents a remarkable "snapshot" from a Berriasian (Early Cretaceous) ecosystem and offers a unique opportunity to study intraspecific variation among a herd of at least 61 coeval ornithomimosaurs. Herein, we investigated the hindlimb variation across the best-preserved specimens from the herd through 3D Geometric Morphometrics and Gaussian Mixture Modelling. Our results based on complete and fragmented femora evidenced a dimorphism characterized by variations in the shaft curvature and the distal epiphysis width. Since the same features vary between sexes among modern avian dinosaurs, crocodilians, and more distant amniotes, we attributed this bimodal variation to sexual dimorphism based on the extant phylogenetic bracketing approach. Documenting sexual dimorphism in fossil dinosaurs allows a better characterization and accounting of intraspecific variations, which is particularly relevant to address ongoing taxonomical and ecological questions relative to dinosaur evolution.

Source connections

Explore related subjects

paleontologyPreprint

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

Pintore, R., Cornette, R., Houssaye, A., Allain, R.. 2022-09-21. Femora from an exceptionally large population of coeval ornithomimosaurs yield evidence of sexual dimorphism in extinct theropod dinosaurs. https://doi.org/10.1101/2022.09.20.508522

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related preprints

bioRxiv2026

Unique pattern of injuries in Olenoides serratus from the Burgess Shale elucidate moulting process in trilobites

Ecdysozoans is one of the most abundant and diverse groups of metazoans and grow through moulting the rigid exoskeleton that provided protection. But the moulting process is often dangerous, resulting in malformations or death. Injuries have been well documented in the calcitic exoskeleton of trilobites, some of which have been attributed to moulting complications when long spines are deformed. Injuries in trilobites are often found in the trunk rather than the cephalon, and abnormal genal spines are rarely documented. Here we examine injuries in eleven specimens of Olenoides serratus from the Burgess Shale (Cambrian, Wuluian) and demonstrate an increased frequency of genal spine malformations compared to other trilobites. The unusual pattern of malformations may be attributed to moulting injuries of the long and delicate genal spines in O. serratus. To moult, trilobites curved ventrally to press the anterior margin of their cephalon into the substrate and open the facial sutures. This process exerted force on the librigenae. To exit the exuvia, the genal spines were forced to bend as the old librigenae dipped ventrally along the anterior edge, resulting in the injured genal spines in O. serratus. A similar process of moulting resulting in injuries may be seen in other early Euarthropods.

paleontology↗
bioRxiv2026

Bone diagenesis in Iron Age Siberia: a histological and microtomographic study of Tunnug 1 (Russia, 2nd-4th c. CE)

The Siberian site of Tunnug 1, located in the Uyuk Valley (Tuva Republic, Russia), encompasses an Early Scythian burial mound (9th century BCE) and a peripheral cemetery attributed to the Kokel culture (2nd-4th centuries CE). Situated within a permafrost-affected environment, the site offers an opportunity to investigate bone preservation under long-term freeze-thaw cycle conditions and explore the relationship between funerary treatment and bone diagenesis. This study presents a combined histological and microtomographic analysis of 76 bone samples from 71 individuals across 36 burials. Transmitted light microscopy, scanning electron microscopy (SEM) and micro-computed tomography (micro-CT) were employed to document biological, chemical and physical degradation. Bone preservation was evaluated through three approaches: the traditional Oxford Histological Index (OHI), quantitative image analysis and assessment of (micro)cracking. The results revealed moderate bone preservation (OHI 2-4). Biological degradation in the form of Microscopical Focal Destruction (MFD) and chemical alteration were identified in six individuals. Enlarged canaliculi were observed in every bone sample. Microcracks were present in all individuals, visible exclusively under SEM. No clear diagenetic signatures linked to specific funerary practices were identified, though variations in preservation suggest a possible influence of burial depth. The distinct impact of permafrost and long-term freeze-thaw cycles on bone microstructure could not be isolated, underscoring the multifactorial nature of diagenesis. This study highlights the complementary value of combining multiple analytical methods assessing bone diagenesis and emphasises the need for continued experimental research into the effects of freezing environments on human remains.

paleontology↗
bioRxiv2026

NOTE ON RHEIFORMES (AVES: PALAEOGNATHAE) FROM A QUATERNARY CAVE IN THE LAGOA SANTA KARST, EASTERN BRAZIL

Rheiformes are a South American lineage of large, flightless palaeognathous birds, currently represented by the genus Rhea and the two extant species R. americana and R. pennata. The fossil record of the group extends back to the Eocene, with its greatest diversification occurring during the Neogene. During the Quaternary, Rheiformes were widely distributed across southern and central South America. The Lagoa Santa region is particularly notable for its rich paleontological and archaeological record. Quaternary records of Rheiformes from caves in this region provide important evidence for understanding the distribution of the group in Brazil, although their chronological context remains uncertain owing to the absence of direct dating. Here, we describe and illustrate two rheiform bones recovered from a cave in the Lagoa Santa karst region. The material comprises a partially complete tibiotarsus and a fragmented tarsometatarsus, interpreted as belonging to a single individual. Comparative anatomical and morphometric analyses support their attribution to Rhea americana, based on morphological features and dimensions consistent with adult specimens of the species. This occurrence extends the Quaternary record of Rheiformes in the Lagoa Santa region and contributes to the fossil and subfossil record of Rhea in Brazil. The absence of stratigraphic and geochronological control precludes a precise age determination. Although the association with an extinct dasypodid indicates the presence of Late Pleistocene or Early Holocene faunal elements at the locality, a Holocene or even recent age for the rheiform remains cannot be excluded.

paleontology↗