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Lowie A, De Kegel B, Wilkinson M, Measey J, O'Reilly JC, Kley NJ, Gaucher P, Brecko J, Kleinteich T, Adriaens D, Herrel A. Is vertebral shape variability in caecilians (Amphibia: Gymnophiona) constrained by forces experienced during burrowing? J Exp Biol 2022; 225:275610. [PMID: 35662342 DOI: 10.1242/jeb.244288] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2022] [Accepted: 05/18/2022] [Indexed: 11/20/2022]
Abstract
Caecilians are predominantly burrowing, elongate, limbless amphibians that remain relatively poorly studied. Although it has been suggested that the sturdy and compact skulls of caecilians are an adaptation to their head-first burrowing habits, no clear relationship between skull shape and burrowing performance appears to exist. However, the external forces encountered during burrowing are transmitted by the skull to the vertebral column, and as such, may impact vertebral shape. Additionally, the muscles that generate the burrowing forces attach onto the vertebral column and consequently may impact vertebral shape that way as well. Here, we explore the relationships between vertebral shape and maximal in vivo push forces in 13 species of caecilian amphibians. Our results show that the shape of the two most anterior vertebrae, as well as the shape of the vertebrae at 90% of the total body length, are not correlated with peak push forces. Conversely, the shape of the third vertebrae, and the vertebrae at 20% and 60% of the total body length, do show a relationship to push forces measured in vivo. Whether these relationships are indirect (external forces constraining shape variation) or direct (muscles forces constraining shape variation) remains unclear and will require quantitative studies of the axial musculature. Importantly, our data suggest that mid-body vertebrae may potentially be used as proxies to infer burrowing capacity in fossil representatives.
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Affiliation(s)
- Aurélien Lowie
- Ghent University, Department of Biology, Evolutionary Morphology of Vertebrates, K.L. Ledeganckstraat 35, 9000 Gent, Belgium
| | - Barbara De Kegel
- Ghent University, Department of Biology, Evolutionary Morphology of Vertebrates, K.L. Ledeganckstraat 35, 9000 Gent, Belgium
| | - Mark Wilkinson
- Department of Life Sciences, Natural History Museum, London SW7 5BD, UK
| | - John Measey
- Centre for Invasion Biology, Department of Botany & Zoology, Stellenbosch University, Private Bag X1, 7602 Matieland, Stellenbosch, South Africa
| | - James C O'Reilly
- Department of Biomedical Sciences, Ohio University, Cleveland Campus, SPS-334C, Cleveland, OH 45701, USA
| | - Nathan J Kley
- Department of Anatomical Sciences, Health Sciences Center, T8-082, Stony Brook University, Stony Brook, NY 11794-8081, USA
| | - Philippe Gaucher
- USR 3456, CNRS, Centre de recherche de Montabo IRD, CNRS-Guyane, 97334 Cayenne, French Guiana
| | - Jonathan Brecko
- Royal Museum for Central Africa, Biological Collections and Data Management, 3080 Tervuren, Belgium
| | | | - Dominique Adriaens
- Ghent University, Department of Biology, Evolutionary Morphology of Vertebrates, K.L. Ledeganckstraat 35, 9000 Gent, Belgium
| | - Anthony Herrel
- Ghent University, Department of Biology, Evolutionary Morphology of Vertebrates, K.L. Ledeganckstraat 35, 9000 Gent, Belgium.,UMR 7179 C.N.R.S/M.N.H.N., Département d'Ecologie et de Gestion de la Biodiversité, 57 rue Cuvier, Case postale 55, 75231, Paris Cedex 5, France
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Benito J, Chen A, Wilson LE, Bhullar BAS, Burnham D, Field DJ. Forty new specimens of Ichthyornis provide unprecedented insight into the postcranial morphology of crownward stem group birds. PeerJ 2022; 10:e13919. [PMID: 36545383 PMCID: PMC9762251 DOI: 10.7717/peerj.13919] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2021] [Accepted: 07/28/2022] [Indexed: 12/23/2022] Open
Abstract
Ichthyornis has long been recognized as a pivotally important fossil taxon for understanding the latest stages of the dinosaur-bird transition, but little significant new postcranial material has been brought to light since initial descriptions of partial skeletons in the 19th Century. Here, we present new information on the postcranial morphology of Ichthyornis from 40 previously undescribed specimens, providing the most complete morphological assessment of the postcranial skeleton of Ichthyornis to date. The new material includes four partially complete skeletons and numerous well-preserved isolated elements, enabling new anatomical observations such as muscle attachments previously undescribed for Mesozoic euornitheans. Among the elements that were previously unknown or poorly represented for Ichthyornis, the new specimens include an almost-complete axial series, a hypocleideum-bearing furcula, radial carpal bones, fibulae, a complete tarsometatarsus bearing a rudimentary hypotarsus, and one of the first-known nearly complete three-dimensional sterna from a Mesozoic avialan. Several pedal phalanges are preserved, revealing a remarkably enlarged pes presumably related to foot-propelled swimming. Although diagnosable as Ichthyornis, the new specimens exhibit a substantial degree of morphological variation, some of which may relate to ontogenetic changes. Phylogenetic analyses incorporating our new data and employing alternative morphological datasets recover Ichthyornis stemward of Hesperornithes and Iaceornis, in line with some recent hypotheses regarding the topology of the crownward-most portion of the avian stem group, and we establish phylogenetically-defined clade names for relevant avialan subclades to help facilitate consistent discourse in future work. The new information provided by these specimens improves our understanding of morphological evolution among the crownward-most non-neornithine avialans immediately preceding the origin of crown group birds.
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Affiliation(s)
- Juan Benito
- Department of Biology & Biochemistry, Milner Centre for Evolution, University of Bath, Bath, United Kingdom.,Department of Earth Sciences, University of Cambridge, Cambridge, Cambridgeshire, United Kingdom
| | - Albert Chen
- Department of Biology & Biochemistry, Milner Centre for Evolution, University of Bath, Bath, United Kingdom.,Department of Earth Sciences, University of Cambridge, Cambridge, Cambridgeshire, United Kingdom
| | - Laura E Wilson
- Fort Hays State University, Sternberg Museum of Natural History and Department of Geosciences, Hays, Kansas, United States
| | - Bhart-Anjan S Bhullar
- Yale Peabody Museum of Natural History, New Haven, Conneticut, United States.,Department of Earth & Planetary Sciences, Yale University, New Haven, Conneticut, United States
| | - David Burnham
- University of Kansas, Biodiversity Institute and Natural History Museum, Lawrence, Kansas, United States
| | - Daniel J Field
- Department of Earth Sciences, University of Cambridge, Cambridge, Cambridgeshire, United Kingdom.,University Museum of Zoology, Cambridge, United Kingdom
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Marigó J, Roig I, Seiffert ER, Moyà-Solà S, Boyer DM. Astragalar and calcaneal morphology of the middle Eocene primate Anchomomys frontanyensis (Anchomomyini): Implications for early primate evolution. J Hum Evol 2016; 91:122-43. [PMID: 26852816 DOI: 10.1016/j.jhevol.2015.08.011] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2014] [Revised: 07/07/2015] [Accepted: 08/29/2015] [Indexed: 10/22/2022]
Abstract
Astragali and calcanei of Anchomomys frontanyensis, a small adapiform from the middle Eocene of Sant Jaume de Frontanyà (Southern Pyrenean basins, northeastern Spain) are described in detail. Though these bones have been known for some time, they have never been carefully analyzed in a context that is comprehensively comparative, quantitative, considers sample variation (astragalus n = 4; calcaneus n = 16), and assesses the phylogenetic significance of the material in an explicit cladistic context, as we do here. Though these bones are isolated, regression analyses provide the first formal statistical support for attribution to A. frontanyensis. The astragalus presents features similar to those of the small stem strepsirrhine Djebelemur from the middle Eocene of Tunisia, while the calcaneus more closely resembles those of the basal omomyiform Teilhardina. The new phylogenetic analyses that include Anchomomys' postcranial and dental data recover anchomomyins outside of the adapiform clade, and closer to djebelemurids, azibiids, and crown strepsirrhines. The small size of A. frontanyensis allows comparison of similarly small adapiforms and omomyiforms (haplorhines) such that observed variation has more straightforward implications for function. Previous studies have demonstrated that distal calcaneal elongation is reflective of leaping proclivity when effects of body mass are appropriately accounted for; in this context, A. frontanyensis has calcaneal elongation suggesting a higher degree of leaping specialization than other adapiforms and even some early omomyiforms. Moreover, comparison to a similarly-sized early adapiform from India, Marcgodinotius (which shows no calcaneal elongation) confirms that high distal calcaneal elongation in A. frontanyensis cannot be simply explained by allometric effects of small size compared to larger adapiform taxa. This pattern is consistent with the idea that significant distal calcaneal elongation evolved at least twice in early euprimates, and that early primate niche space frequently included demands for increased leaping specialization.
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Affiliation(s)
- Judit Marigó
- Department of Evolutionary Anthropology, Duke University, Durham, NC, USA; Institut Català de Paleontologia Miquel Crusafont (ICP), Universitat Autònoma de Barcelona, Edifici Z (ICTA-ICP), Carrer de les Columnes s/n, Campus UAB, 08193 Cerdanyola del Vallès, Barcelona, Spain.
| | - Imma Roig
- Institut Català de Paleontologia Miquel Crusafont (ICP), Universitat Autònoma de Barcelona, Edifici Z (ICTA-ICP), Carrer de les Columnes s/n, Campus UAB, 08193 Cerdanyola del Vallès, Barcelona, Spain
| | - Erik R Seiffert
- Department of Anatomical Sciences, Stony Brook University, Stony Brook, NY, USA
| | - Salvador Moyà-Solà
- ICREA at Institut Català de Paleontologia Miquel Crusafont (ICP), Universitat Autònoma de Barcelona, Edifici Z (ICTA-ICP), Carrer de les Columnes s/n, Campus UAB, 08193 Cerdanyola del Vallès, Barcelona, Spain
| | - Doug M Boyer
- Department of Evolutionary Anthropology, Duke University, Durham, NC, USA
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