Zoology Life sciences: Multidisciplinary, general & others Physical, chemical, mathematical & earth Sciences: Multidisciplinary, general & others
Author, co-author :
Palmer, Stephanie; JHU - Johns Hopkins University [US-MD] > Center for Functional Anatomy and Evolution
Chatar, Narimane ; UCB - University of California Berkeley [US-CA] > Integrative Biology
Rule, James; Natural History Museum, London > Sciences Group
Vankelst, Melvin ; Université de Liège - ULiège > Faculté des Sciences > Master biol. orga. & écol., fin. approf. ; ULiège - Université de Liège [BE] > Evolution and Diversity Dynamics Lab
Cooke, Siobhan; JHU - Johns Hopkins University [US-MD] > Center for Functional Anatomy and Evolution
Language :
English
Title :
Homodonty evolved after the aquatic transition in Pinnipedia
Publication date :
26 June 2024
Event name :
10th SECAD meeting
Event organizer :
Evolution and Diversity Dynamics Lab
Event place :
Liège, Belgium
Event date :
25-28 June 2024
Audience :
International
Peer reviewed :
Peer reviewed
References of the abstract :
Homodonty of the postcanine dental row is a distinctive trait characteristic of the secondarily aquatic tetrapods and is correlated with aquatic prey capture strategies. This study quantifies pinniped postcanine dental size and shape in order to reconstruct patterns of postcanine homodonty and its relationship with the evolution of aquatic feeding. Using a sample of extant pinnipeds (n=25), fossil crown pinnipeds (n=6), stem pinnipeds Enaliarctos barnesi (n=1) and Semantoridae (n=3), and caniform outgroup taxa (fissipeds; n=5), we quantify the morphology of the mandibular second premolar through the first molar using linear measurements (crown length, width, height), mesh volumes, and dental topographic metrics (DTM) orientation patch count rotated (OPCR) and Convex Dirichlet normal energy (CDNE). Coefficients of variation (CVs) for each variable were calculated per specimen as a proxy for homodonty. CVs for nine traits were analyzed using Principal Component Analysis (PCA) to reduce dimensionality of the dataset and visualize major components of variation. A total of four PCAs were conducted separately using all variables and excluding DTM, volume, and non-ratioed linear measurements. Variables driving PC1 loadings were then tested for differences between extant pinnipeds, fissipeds, and Semantoridae using pairwise comparisons (Tukey and Mann-Whitney tests). Variance captured by PC1 ranged from 92% to 74.9%. PC1 consistently separated extant pinnipeds, fossil crown pinnipeds, and Enaliarctos from fissiped outgroup taxa, with Semantoridae plotting either intermediately between them or within pinniped space. Traits driving variation included CVs of mesh volume, OPCR, mesio-distal length, and height relative to crown base area. Semantoridae significantly differed from both fissiped outgroup taxa and extant pinnipeds for each metric except for relative height, where it differed from fissipeds only. Semantoridae differs from fissipeds in having proportionally smaller teeth that are more equal in size, while differentiation in shape more closely aligns with the fissiped condition. This may reflect shifts away from relative reliance of the m1 and premolars for mastication. These results suggest that early transitional stages towards homodonty primarily involved variations in relative tooth size, while shifts in shape occurred subsequently. Finally, homodonty akin to that observed in crown pinnipeds emerged in enaliarctines, evolving subsequent to the aquatic transition.
Funding Acknowledgements: SMP was supported by a Los Angeles County Museum of Natural History Student Travel Grant, JPR was supported by an Engineering and Physical Sciences Research Council UKRI Fellowship (grant no. EP/X021238/1).
