10.5061/DRYAD.8JH08MP
Griebeler, Eva Maria
University Medical Center of the Johannes Gutenberg University Mainz
Klein, Nicole
Staatliches Museum für Naturkunde Stuttgart
Data from: Life-history strategies indicate live-bearing in Nothosaurus
(Sauropterygia)
Dryad
dataset
2019
Nothosaurus
birth-to-adult size ratio
Squamata
Pachypleurosauria
bone histology
Viviparity
2019-03-14T17:35:29Z
2019-03-14T17:35:29Z
en
https://doi.org/10.1111/pala.12425
6664503 bytes
1
CC0 1.0 Universal (CC0 1.0) Public Domain Dedication
In Sauropterygia, a diverse group of Mesozoic marine reptiles, fossil
evidence of viviparity (live‐bearing) only exists for Pachypleurosauria
and Plesiosauria, and was assumed to also be the case for nothosaurs.
Previous studies have successfully applied an extant squamate model to
sauropterygian life‐history traits. In extant squamates, oviparity and
viviparity are associated with differences in life‐history trait
combinations. We establish growth curves for Nothosaurus specimens based
on their humeral histology. We then analyse life‐history traits derived
from these curves and compare inferred traits to those of modern squamates
and pachypleurosaurs to assess their reproduction mode. We show that birth
to adult size ratios (i.e. birth size divided by the mother's size)
provide good estimates of clutch sizes in extant squamates and in
viviparous extinct marine reptiles, but these ratios cannot discriminate
viviparous and oviparous squamates. Thus, large ratios do not indicate
viviparity in fossil taxa to which the extant squamate model is
applicable. Applying differences in birth size, age at maturation, and
maximum longevity that are observed between extant viviparous and
oviparous squamates to our Nothosaurus sample, we identified 7 out of 24
specimens as being potentially viviparous. Conversely, they suggested
oviparity for many nothosaurs but also for many pachypleurosaur samples.
Under the assumption that the entire clade Pachypleurosauria was
viviparous, the majority of nothosaurs would also have been viviparous as
they comprised trait combinations similar to those seen in
pachypleurosaurs. Overall, this suggests that within nothosaurs and
pachypleurosaurs both reproduction modes existed in different taxa.
Griebeler_Klein_Supplementary_InformationSupporting Information with
growth records of nothosaurs, additional statistical analysis on
differences in life-history strategies of extant squamates, a detailed
description of our growth curve fitting method, tables with equations
fitted to the growth record of nothosaur specimens, and life-history
traits inferred from nothosaur growth curves.
Germanic Basin