bioRxiv Science⌕ Search
Home/Archive/bioRxiv

bioRxiv · 10.1101/2024.02.15.578844

Body reconstruction and size estimation of plesiosaurs

Zhao, R. J.
View original source ↗Export metadata ↓

Abstract

Body size, especially body mass, is the key to understanding many biological properties. The scaling approaches and volumetric-density (VD) approaches are often employed to estimate the body masses of extinct amniotes. Precise skeletal reconstruction represents a pivotal step in all VD approaches, while the ribcage serves as one of the key determinants of thoracic shape and volume. Although being extensively investigated in physiological studies, the ribcage restoration remains poorly discussed during skeletal reconstruction. This study proposes one possible programme of skeletal reconstruction of extinct amniotes in 2D environments, focusing on the restoration of ribcage cross-sections. One recent VD approach, the cross-sectional method (CSM), was utilized to integrate the restored cross-sections into volume, therefore the workflow proposed here serves as a supplementary guideline of the application of the CSM in paleontology. Following this programme, a uniform set of reconstruction criteria was proposed for plesiosaurs, a clade of Mesozoic marine reptiles. Twenty-four plesiosaur models were created, then multiple regression models (Ordinary Least Squares, OLS; and Phylogenetically Generalized Least Squares, PGLS) based on them were employed to investigate the performance of various skeletal elements as size proxy. Despite the high disparity of their body plans, the trunk length and dimensions of dorsal vertebrae were found to be the most robost proxy for volume in plesiosaurs. The hybrid approach applied in this study, which incorporates VD estimates created under the same criteria as scaling samples, mitigates previous critiques focusing on inconsistent standards and inadequate taxonomic coverage. It allows fast and convenient body volume estimation for numerus individuals, even when only fragmentary fossil materials are available. The volumetric formulae for plesiosaurs can accommodate the size diversity of most taxa, except for some extremely giant pliosaurs, the largest of which might reach or exceed 20 metric tons in body mass. To demonstrate the utility of the formulae provided in this study, the body volumes of 113 plesiosaur taxa was estimated, and the branch-specific rates of size evolution computed from the data were mapped onto a plesiosaur phylogeny for visualization.

Source connections

Explore related subjects

paleontologyPreprint

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

Zhao, R. J.. 2024-02-19. Body reconstruction and size estimation of plesiosaurs. https://doi.org/10.1101/2024.02.15.578844

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

KEEP EXPLORING

Related preprints

bioRxiv2026

Constraining Palaeogeography and Palaeotides for the Cambrian using cnidarian medusae

The ocean tides influence key Earth system processes at a range of spatial and temporal scales. It is known that the geometry of ocean basins is the leading controller of tidal energetics, so well-constrained palaeogeographic reconstructions and tidal properties for Earths past are imperative when investigating other Earth system processes. Here, we present a novel way to constrain both deep-time tidal model results and reconstructions, by combining palaeoecology with sedimentology. We compare new palaeo-tidal model simulations for the Cambrian period, significant for the early origin and radiation of major animal fauna, to tidal proxies. One of the most abundant soft-bodied organisms preserved during this time are cnidarian medusae (jellyfish). A total of 17 cnidarian medusae localities were obtained through the literature, which had an adequate global distribution and occurred at regular intervals throughout the period of study. In some locations there were also estimates of palaeo-tidal range. Our results show a good agreement between the simulations and proxy data. In the few locations where there is disagreement, it is proposed that the palaeogeographic reconstructions are missing details, e.g., island chains, and our results allow for the palaeogeographic reconstructions to be improved. The proxy method presented is promising and can be applied to other time-periods with different marine fossils, particularly at evolutionary and extinction periods where the marginal marine environment is of importance.

paleontology↗
bioRxiv2025

Non-destructive radiocarbon dating of bone

Since the 1950s, radiocarbon measurements have anchored archaeological chronologies dating back to 50,000 years, with bone collagen being a commonly dated material. Despite advances in collagen extraction protocols, the process remains destructive, requiring sampling by sawing, drilling or crushing of dry bone, that can damage or destroy physical features and archaeological evidence, and often consumes the entire specimen. While non-destructive approaches have recently been applied in ancient genomics and palaeoproteomics, no equivalent approach has been established for radiocarbon dating of bone. Here, we outline a non-destructive collagen extraction workflow that avoids invasive sampling (cutting or drilling) and produces no visible damage to the bone. By heating the bone in hot water for several hours, collagen is solubilized, and the resulting collagenous solution can be purified and AMS dated. Here we show that the amino acid composition, C/N atomic ratios, {delta}13C and {delta}15N values of the hot-water-extracted collagen are comparable to collagen isolated from the same bones using classic decalcification methodologies. The hot water extraction method was tested on various bones, ranging from the Bronze Age to the Middle and Upper Paleolithic periods, which had been dated previously using routine destructive methods that involved acid demineralization. Our results show that non-destructive collagen extraction, coupled with an additional purification step e.g., ultrafiltration, yields identical radiocarbon ages to those obtained via the routine destructive methods.

paleontology↗
bioRxiv2025

Archaeological Bone Assemblages Trace Changes in Turtle and Tortoise Diversity in Continental Southeast Asia

Among tropical regions, continental Southeast Asia is a major hotspot of biodiversity. However, due to rapid urban expansion and severe deforestation, this area is recognized as one of the top global conservation priorities. As in other tropical regions, the prevailing idea is that the decline of local biodiversity in this region is a direct result of the overwhelming environmental changes that have occurred over the last 80 years. However, paleoecological data indicate that tropical forests have been exploited by human populations since at least the Late Pleistocene, and forest clearance for farming began several thousand years ago. To gain a complete overview of the long-term evolution of vertebrate fauna in continental Southeast Asia, it is necessary to investigate the past. This task is currently out of reach, mainly due to the lack of paleontological and historical studies regarding small animals, including emblematic taxa like turtles. Indeed, although some evidence suggests that the biodiversity of turtles in continental Southeast Asia may have changed over the last millennia, the paucity of historical records and archaeological assemblages studies currently precludes further assessment of the potential effect of past environmental changes, including potential human disturbances. The present study consists of a paleontological analysis of turtle bone assemblages collected from four prehistoric sites in Thailand and Cambodia. The aim is to test the hypothesis of changes in turtle biodiversity over the last 10,000 years. Our results indicate that turtle assemblages in most areas have experienced only limited changes across the Holocene, except for Laang Spean in Cambodia. However, a few rare taxa may represent extirpated or extinct species of Testudinidae in continental Southeast Asia at an unknown time during the Holocene. We also observed significant changes in the geographic distribution of some genera, such as Batagur, Cyclemys, and Amyda. The fact that turtle fauna has been rather resilient and unchanged for several millennia shows that past human impact in most investigated areas had limited effects on these taxa. The strong modifications observed in Cambodia could, however, serve as a warning about the potential fate of turtle biodiversity in this region if further loss of natural environments occurs.

paleontology↗