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Putative avian teeth from the Late Cretaceous of Alberta, Canada, are more likely from crocodilians
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Abstract
Isolated teeth, previously referred to Aves, are more common than other bird fossils from the Late Cretaceous of Alberta. However, there are no known morphological synapomorphies that distinguish isolated bird teeth, and features of these teeth are generally shared with those of non-avian theropods and crocodilians. Here, specimens ranging from Late Santonian to Late Maastrichtian in age are described and qualitatively categorized into morphotypes, most of which strongly resemble teeth of extant juvenile and some fossil crocodilians. Variation within this sample of teeth may therefore reflect the heterodont dentition of crocodilians, rather than avian species diversity. Quantitative analysis Principal Component Analysis was mostly uninformative, with limited overlap between putative avian teeth and those of known Cretaceous birds, crocodilians, and non-avian theropods. The reassignment of these putative avian teeth to Crocodylia has important ramifications for our understanding of the evolutionary history of Cretaceous birds.
Related collections
Most cited references46
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Mass extinction of birds at the Cretaceous-Paleogene (K-Pg) boundary.
Nicholas R Longrich, Tim Tokaryk, R. Field (2011)
The effect of the Cretaceous-Paleogene (K-Pg) (formerly Cretaceous-Tertiary, K-T) mass extinction on avian evolution is debated, primarily because of the poor fossil record of Late Cretaceous birds. In particular, it remains unclear whether archaic birds became extinct gradually over the course of the Cretaceous or whether they remained diverse up to the end of the Cretaceous and perished in the K-Pg mass extinction. Here, we describe a diverse avifauna from the latest Maastrichtian of western North America, which provides definitive evidence for the persistence of a range of archaic birds to within 300,000 y of the K-Pg boundary. A total of 17 species are identified, including 7 species of archaic bird, representing Enantiornithes, Ichthyornithes, Hesperornithes, and an Apsaravis-like bird. None of these groups are known to survive into the Paleogene, and their persistence into the latest Maastrichtian therefore provides strong evidence for a mass extinction of archaic birds coinciding with the Chicxulub asteroid impact. Most of the birds described here represent advanced ornithurines, showing that a major radiation of Ornithurae preceded the end of the Cretaceous, but none can be definitively referred to the Neornithes. This avifauna is the most diverse known from the Late Cretaceous, and although size disparity is lower than in modern birds, the assemblage includes both smaller forms and some of the largest volant birds known from the Mesozoic, emphasizing the degree to which avian diversification had proceeded by the end of the age of dinosaurs.
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The smallest known non-avian theropod dinosaur.
Xing Xu, Zhonghe Zhou, Xiaolin Wang (2000)
Non-avian dinosaurs are mostly medium to large-sized animals, and to date all known mature specimens are larger than the most primitive bird, Archaeopteryx. Here we report on a new dromaeosaurid dinosaur, Microraptor zhaoianus gen. et sp. nov., from the Early Cretaceous Jiufotang Formation of Liaoning, China. This is the first mature non-avian dinosaur to be found that is smaller than Archaeopteryx, and it eliminates the size disparity between the earliest birds and their closest non-avian theropod relatives. The more bird-like teeth, the Rahonavis-like ischium and the small number of caudal vertebrae of Microraptor are unique among dromaeosaurids and improve our understanding of the morphological transition to birds. The nearly completely articulated foot shows features, such as distally positioned digit I, slender and recurved pedal claws, and elongated penultimate phalanges, that are comparable to those of arboreal birds. The discovery of these in non-avian theropods provides new insights for studying the palaeoecology of some bird-like theropod dinosaurs.
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A theropod dinosaur embryo and the affinities of the flaming cliffs dinosaur eggs.
M. A. Norell, J M Clark, D Demberelyin … (1994)
An embryonic skeleton of a nonavian theropod dinosaur was found preserved in an egg from Upper Cretaceous rocks in the Gobi Desert of Mongolia. Cranial features identify the embryo as a member of Oviraptoridae. Two embryo-sized skulls of dromaeosaurids, similar to that of Velociraptor, were also recovered in the nest. The eggshell microstructure is similar to that of ratite birds and is of a type common in the Djadokhta Formation at the Flaming Cliffs (Bayn Dzak). Discovery of a nest of such eggs at the Flaming Cliffs in 1923, beneath the Oviraptor philoceratops holotype, suggests that this dinosaur may have been a brooding adult.
Author and article information
Contributors
Sydney R. Mohr:
ORCID: https://orcid.org/0000-0003-1327-8223
Role: Data curationRole: Formal analysisRole: Funding acquisitionRole: InvestigationRole:
VisualizationRole: Writing – original draftRole: Writing – review & editing
John H. Acorn:
ORCID: https://orcid.org/0000-0001-6570-1949
Role: ConceptualizationRole: MethodologyRole: SupervisionRole: Writing – review &
editing
Philip J Currie: Role: SupervisionRole: Writing – review & editing
Paolo Piras: Role: Editor
Journal
Journal ID (nlm-ta): PLoS One
Journal ID (iso-abbrev): PLoS One
Journal ID (publisher-id): plos
Title:
PLOS ONE
Publisher:
Public Library of Science
(San Francisco, CA USA
)
ISSN
(Electronic):
1932-6203
Publication date
(Electronic):
28
March
2023
Publication date Collection: 2023
Volume: 18
Issue: 3
Electronic Location Identifier: e0283581
Affiliations
Author notes
* E-mail:
smohr@
123456ualberta.ca
Author information
Sydney R. Mohr
https://orcid.org/0000-0003-1327-8223
John H. Acorn
https://orcid.org/0000-0001-6570-1949
Article
Publisher ID: PONE-D-22-17488DOI: 10.1371/journal.pone.0283581
PMC ID: 10047536
SO-VID: 145a3ab0-a3da-4602-ae1c-2c79727c360c
Copyright © © 2023 Mohr et al
License:
This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
History
Date
received
: 18
June
2022
Date
accepted
: 13
March
2023
Page count
Figures: 5,
Tables: 2,
Pages: 18
Funding
Funded by:
NSERC PGS-D
Award Recipient
:
ORCID: https://orcid.org/0000-0003-1327-8223
Sydney R Mohr
Funded by:
Queen Elizabeth II Scholarship
Award Recipient
:
ORCID: https://orcid.org/0000-0003-1327-8223
Sydney R Mohr
Funded by:
funder-id http://dx.doi.org/10.13039/100012268, Alberta Historical Resources Foundation;
Award Recipient
:
ORCID: https://orcid.org/0000-0003-1327-8223
Sydney R Mohr
Funded by:
Alberta Lottery Fund
Award Recipient
:
ORCID: https://orcid.org/0000-0003-1327-8223
Sydney R Mohr
Funded by:
funder-id http://dx.doi.org/10.13039/501100020304, Dinosaur Research Institute;
Award Recipient
:
ORCID: https://orcid.org/0000-0003-1327-8223
Sydney R Mohr
Funded by:
funder-id http://dx.doi.org/10.13039/501100000038, Natural Sciences and Engineering Research Council of Canada;
Award ID: RGPIN-2017- 04715
Award Recipient
:
Philip J Currie
S.R.M. was funded by the Queen Elizabeth II Graduate Scholarship, Dinosaur Research
Institute, Alberta Historical Resources Foundation, Alberta Lottery Fund, and Natural
Sciences and Engineering Research Council (NSERC) PGS-D. P.J.C is supported by Natural
Sciences and Engineering Research Council (NSERC) [Grant # RGPIN-2017- 04715]. The
funders had no role in study design, data collection and analysis, decision to publish,
or preparation of the manuscript.
Categories
Subject:
Research Article
Subject:
Biology and Life Sciences
Subject:
Anatomy
Subject:
Digestive System
Subject:
Teeth
Subject:
Medicine and Health Sciences
Subject:
Anatomy
Subject:
Digestive System
Subject:
Teeth
Subject:
Biology and Life Sciences
Subject:
Anatomy
Subject:
Head
Subject:
Jaw
Subject:
Teeth
Subject:
Medicine and Health Sciences
Subject:
Anatomy
Subject:
Head
Subject:
Jaw
Subject:
Teeth
Subject:
Biology and Life Sciences
Subject:
Physiology
Subject:
Digestive Physiology
Subject:
Dentition
Subject:
Biology and Life Sciences
Subject:
Organisms
Subject:
Eukaryota
Subject:
Animals
Subject:
Vertebrates
Subject:
Amniotes
Subject:
Birds
Subject:
Biology and Life Sciences
Subject:
Zoology
Subject:
Animals
Subject:
Vertebrates
Subject:
Amniotes
Subject:
Birds
Subject:
Biology and Life Sciences
Subject:
Organisms
Subject:
Eukaryota
Subject:
Animals
Subject:
Prehistoric Animals
Subject:
Archosauria
Subject:
Dinosaurs
Subject:
Saurischia
Subject:
Theropoda
Subject:
Biology and Life Sciences
Subject:
Zoology
Subject:
Animals
Subject:
Prehistoric Animals
Subject:
Archosauria
Subject:
Dinosaurs
Subject:
Saurischia
Subject:
Theropoda
Subject:
Biology and Life Sciences
Subject:
Paleontology
Subject:
Prehistoric Animals
Subject:
Archosauria
Subject:
Dinosaurs
Subject:
Saurischia
Subject:
Theropoda
Subject:
Earth Sciences
Subject:
Paleontology
Subject:
Prehistoric Animals
Subject:
Archosauria
Subject:
Dinosaurs
Subject:
Saurischia
Subject:
Theropoda
Subject:
Biology and Life Sciences
Subject:
Paleontology
Subject:
Paleobiology
Subject:
Paleozoology
Subject:
Vertebrate Paleontology
Subject:
Prehistoric Animals
Subject:
Archosauria
Subject:
Dinosaurs
Subject:
Saurischia
Subject:
Theropoda
Subject:
Earth Sciences
Subject:
Paleontology
Subject:
Paleobiology
Subject:
Paleozoology
Subject:
Vertebrate Paleontology
Subject:
Prehistoric Animals
Subject:
Archosauria
Subject:
Dinosaurs
Subject:
Saurischia
Subject:
Theropoda
Subject:
Biology and Life Sciences
Subject:
Paleontology
Subject:
Paleobiology
Subject:
Earth Sciences
Subject:
Paleontology
Subject:
Paleobiology
Subject:
Earth Sciences
Subject:
Geology
Subject:
Geologic Time
Subject:
Mesozoic Era
Subject:
Cretaceous Period
Subject:
Research and Analysis Methods
Subject:
Mathematical and Statistical Techniques
Subject:
Statistical Methods
Subject:
Multivariate Analysis
Subject:
Principal Component Analysis
Subject:
Physical Sciences
Subject:
Mathematics
Subject:
Statistics
Subject:
Statistical Methods
Subject:
Multivariate Analysis
Subject:
Principal Component Analysis
Subject:
Biology and Life Sciences
Subject:
Anatomy
Subject:
Head
Subject:
Jaw
Subject:
Medicine and Health Sciences
Subject:
Anatomy
Subject:
Head
Subject:
Jaw
Custom metadata
Data Availability All relevant data are within the paper and its
Supporting Information files.
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Data availability:
ScienceOpen disciplines: Uncategorized