Resolving the "Ontogeny Problem" in Vertebrate Paleontology DOI Open Access
James G. Napoli

bioRxiv (Cold Spring Harbor Laboratory), Journal Year: 2024, Volume and Issue: unknown

Published: Oct. 28, 2024

Abstract Ontogenetic change is a major source of phenotypic variation among members species and often greater magnitude than the anatomical differences that distinguish closely related species. Ontogeny has therefore become problematic confounding variable in vertebrate paleontology, especially study systems distant from extant crown clades, rendering taxonomic hypothesis testing (a fundamental process evolutionary biology) rife with difficulty. Paleontologists have adopted quantitative methods to compensate for perception juvenile specimens lack diagnostic apomorphies seen their adult conspecifics. Here, I critically evaluate these assumptions guide interpretation using µCT dataset comprising growth series American Chinese alligator. find several widespread are scientifically unjustifiable, two popular – geometric morphometrics cladistic analysis ontogeny unacceptably high rates type II error present numerous procedural difficulties. However, also identify suite ontogenetically invariant characters differentiate living Alligator throughout ontogeny. These overwhelmingly correspond develop prior (and play signaling role in) development cranial skeleton itself, suggesting ontogenetic invariance consequence widely conserved developmental program. observations suggest architecture cranium fixed early embryonic development, remodeling does not alter topological relationships bones or soft tissue structures they house. propose general model future tests fossil record, which different stages single can be falsified by discovery character cannot attributed plausibly variation.

Language: Английский

Skull morphology and histology indicate the presence of an unexpected buccal soft tissue structure in dinosaurs DOI Creative Commons
Henry S. Sharpe, Wang Yan-yin, Thomas W. Dudgeon

et al.

Journal of Anatomy, Journal Year: 2025, Volume and Issue: unknown

Published: March 21, 2025

Unlike mammals, reptiles typically lack large muscles and ligaments that connect the zygoma to mandible. Dinosaur craniomandibular soft tissue reconstructions, often based on rationale of extant phylogenetic bracketing, follow this general rule. However, descending flanges from zygomata hadrosaurs, heterodontosaurids, psittacosaurids have been used argue for a masseter-like muscle in these dinosaur taxa. We examined dinosauriform skulls osteological indicators connective entheses mandible, subsequently sectioned 10 specimens histological evidence. Osteological were found most sampled dinosauriforms, which range rugosities processes, morphologically resemble known muscular ligamentous entheses. Similarly, rugose features oriented towards mandible many having previously interpreted as adductor mandibulae group. Serial sectioning ceratopsid, hadrosaurid, tyrannosaurid jugal surangular reveals an external cortex rich collagen fibres, strongly resembling entheseal fibres. Jugal fibres are usually ventrally surangular, hadrosaurids tyrannosaurids parallel macroscopic striations surfaces flange. Histological sections chicken buccal regions show similar attachments jugomandibular ligament musculature hypothesise strong structure bridging dinosaurs, termed 'exoparia'. This structure's size proximity joint would be advantageous stabilising relative cranium during jaw movement, particularly dinosaurs thought process their masticate. A or identity exoparia cannot determined with available data, but shape zygomatic more consistent attachment. Possible antecedents non-dinosauriform archosaurs derivations modern birds may exist, homology is currently unknown. These results highlight complex evolution caution against simplified model-based approaches reconstruction ignore contrasting signals.

Language: Английский

Citations

0
Theropod dinosaur facial reconstruction and the importance of soft tissues in paleobiology DOI Creative Commons
Thomas M. Cullen, Derek W. Larson,

Mark P. Witton

et al.

Science, Journal Year: 2023, Volume and Issue: 379(6639), P. 1348 - 1352

Published: March 31, 2023

Large theropod dinosaurs are often reconstructed with their marginal dentition exposed because of the enormous size teeth and phylogenetic association to crocodylians. We tested this hypothesis using a multiproxy approach. Regressions skull length tooth for range theropods extant varanid lizards confirm that complete coverage dinosaur extraoral tissues (gingiva labial scales) is both plausible consistent patterns observed in living ziphodont amniotes. Analyses dental histology from crocodylians dinosaurs, including Tyrannosaurus rex, further indicate most likely condition was tissue when mouth closed. This changes our perceptions about appearance oral configuration these iconic predators has broad implications interpretations other terrestrial animals large teeth.

Language: Английский

Citations

10
Reassessment of the enigmatic Late Cretaceous theropod dinosaur, Bagaraatan ostromi DOI
Justyna Słowiak, Stephen L. Brusatte, Tomasz Szczygielski

et al.

Zoological Journal of the Linnean Society, Journal Year: 2024, Volume and Issue: 202(3)

Published: Feb. 16, 2024

Abstract The Late Cretaceous Bagaraatan ostromi, described by Osmólska in 1996, is one of the most enigmatic theropod dinosaurs. holotype possesses a peculiar combination features, which suggested were indicative primitive position among theropods that could not be resolved further. Other researchers have pointed to affinities with either derived bird-like coelurosaurs or tyrannosaurids. Here, we reanalyse all material collected Osmólska, reveals it chimaera multiple taxa. femur, tibiotarsus, pedal phalanx, and bones undescribed Osmólska’s paper are identified as Caenagnathidae indet. mandible, cervical vertebrae, pelvis, tail, consider B. show tyrannosaurid affinities, here supported phylogenetic analyses. We find only two potentially unique diagnostic features holotype: double surangular foramina horizontal ridge on lateral surface postacetabular process ilium. Both, however, may ontogenetically intraspecifically variable, thus conclude ostromi represents an indeterminate tyrannosaurid. small size its possession many known characterize juvenile Tyrannosaurus rex indicate skeleton belongs juvenile, smallest tyrannosaurids currently known.

Language: Английский

Citations

2
Mandibular force profiles of Alioramini (Theropoda: Tyrannosauridae) with implications for palaeoecology of this unique lineage of tyrannosaurid dinosaurs DOI Creative Commons
Chan‐gyu Yun

Lethaia, Journal Year: 2024, Volume and Issue: 57(2), P. 1 - 12

Published: June 20, 2024

Language: Английский

Citations

1
The first deep-snouted tyrannosaur from Upper Cretaceous Ganzhou City of southeastern China DOI Creative Commons
Wenjie Zheng,

Xingsheng Jin,

Junfang Xie

et al.

Scientific Reports, Journal Year: 2024, Volume and Issue: 14(1)

Published: July 25, 2024

Tyrannosaurids were the most derived group of Tyrannosauroidea and are characterized by having two body plans: gracile, long-snouted robust, deep-snouted skulls. Both groups lived sympatrically in central Asia. Here, we report a new tyrannosaurid, Asiatyrannus xui gen. et sp. nov., from Upper Cretaceous Ganzhou City, southeastern China, which has produced large-bodied Qianzhousaurus. Based on histological analysis, holotype is not somatically mature adult, but it already passed through rapid growth stages. small to medium-sized tyrannosaurine, with skull length 47.5 cm an estimated total 3.5-4 m; or around half size Qianzhousaurus other tyrannosaurines similar sympatric tyrannosaurid genera Maastrichtian China. differs that proportionally deeper snout, longer premaxilla, maxilla, dentary, cornual process lacrimal inflated without developing discrete horn. The different proportions sizes suggest likely had feeding strategies occupied ecological niches.

Language: Английский

Citations

1
A transitional species of Daspletosaurus Russell, 1970 from the Judith River Formation of eastern Montana DOI Creative Commons
Elías A. Warshaw, Denver W. Fowler

PeerJ, Journal Year: 2022, Volume and Issue: 10, P. e14461 - e14461

Published: Nov. 25, 2022

Here we describe a new derived tyrannosaurine, Daspletosaurus wilsoni sp. nov., from Judithian strata (~76.5 Ma) intermediate in age between either of the previously described species this genus. D. displays unique combination ancestral and characteristics, including cornual process lacrimal reduced height relative to torosus more basal tyrannosaurines, prefrontal with long axis oriented rostrally than horneri tyrannosaurines. The description taxon provides insight into evolutionary mode Tyrannosaurinae, lending strength previous hypotheses anagenesis within increasing resolution which evolution lineage can be reconstructed. Cladistic phylogenetic methods, stratigraphy, qualitative analysis morphology relevant taxa supports an anagenetic model for origin morphological novelty genus, highlighting predominance among contemporary dinosaur lineages.

Language: Английский

Citations

7
A megaraptorid (Dinosauria: Theropoda) frontal from the upper Strzelecki Group (Lower Cretaceous) of Victoria, Australia DOI Creative Commons
Jake Kotevski, Ruairidh J. Duncan, Adele H. Pentland

et al.

Cretaceous Research, Journal Year: 2023, Volume and Issue: 154, P. 105769 - 105769

Published: Nov. 2, 2023

Cretaceous (non-avian) theropod dinosaurs from Australia are poorly understood, primarily because almost all specimens described thus far comprise isolated postcranial elements. In Australia, only three non-dental cranial elements pertaining to Theropoda have been reported: the left and right dentaries of Australovenator wintonensis Winton Formation (Cenomanian–lowermost Turonian) Queensland, an surangular Eumeralla (lower Albian) Victoria. Herein, we report first evidence non-mandibular material a non-avian Australia: frontal fused parietal fragment Lower Aptian) upper Strzelecki Group The specimen shares several synapomorphies with frontals assigned Megaraptoridae, including anteroposteriorly elongate postorbital articulation truncated nasal articular surface. Accordingly, regard this as Megaraptoridae gen. et sp. indet. We performed both parsimony-based Bayesian-based phylogenetic analyses support our assignment, placement within Megaraptoridae. However, appears possess plesiomorphic characters relative other megaraptorid frontals, lacking dorsoventrally high walls bone that emarginate prefrontal surfaces. plesiomorphies implications for evolution megaraptoran skull roof, suggesting acquisition specialised adaptations longirostry over time. This improves limited record Australian remains, provides hypothesis might originated in Australia.

Language: Английский

Citations

3
Resolving the "Ontogeny Problem" in Vertebrate Paleontology DOI Open Access
James G. Napoli

bioRxiv (Cold Spring Harbor Laboratory), Journal Year: 2024, Volume and Issue: unknown

Published: Oct. 28, 2024

Abstract Ontogenetic change is a major source of phenotypic variation among members species and often greater magnitude than the anatomical differences that distinguish closely related species. Ontogeny has therefore become problematic confounding variable in vertebrate paleontology, especially study systems distant from extant crown clades, rendering taxonomic hypothesis testing (a fundamental process evolutionary biology) rife with difficulty. Paleontologists have adopted quantitative methods to compensate for perception juvenile specimens lack diagnostic apomorphies seen their adult conspecifics. Here, I critically evaluate these assumptions guide interpretation using µCT dataset comprising growth series American Chinese alligator. find several widespread are scientifically unjustifiable, two popular – geometric morphometrics cladistic analysis ontogeny unacceptably high rates type II error present numerous procedural difficulties. However, also identify suite ontogenetically invariant characters differentiate living Alligator throughout ontogeny. These overwhelmingly correspond develop prior (and play signaling role in) development cranial skeleton itself, suggesting ontogenetic invariance consequence widely conserved developmental program. observations suggest architecture cranium fixed early embryonic development, remodeling does not alter topological relationships bones or soft tissue structures they house. propose general model future tests fossil record, which different stages single can be falsified by discovery character cannot attributed plausibly variation.

Language: Английский

Citations

0