Premium
Changes in Vertebral Morphology with Increasing Aquatic Adaptation in Crocodylomorphs
Author(s) -
Molnar Julia,
Pierce Stephanie,
Hutchinson John
Publication year - 2015
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.29.1_supplement.345.2
Subject(s) - crocodylus , osteology , morphometrics , crocodile , biology , alligator , anatomy , terrestrial locomotion , trunk , adaptation (eye) , morphology (biology) , zoology , ecology , neuroscience
The lineage leading to modern crocodylians has undergone dramatic evolutionary changes in both morphology and locomotion over the past 200 million years. Our objective was to estimate changes in osteological range of motion (RoM) and intervertebral joint (IVJ) compliance of thoracic and lumbar vertebrae with increasing aquatic adaptation in crocodylomorphs. Using 3D virtual models and morphometrics, we compared the modern crocodile Crocodylus to four extinct crocodylomorphs, Terrestrisuchus, Protosuchus, Pelagosaurus, and Metriorhynchus, which span the spectrum from fully terrestrial to fully aquatic. In Crocodylus , we also experimentally measured changes in trunk flexibility with sequential removal of osteoderms and soft tissues.
Our results showed that both IVJ compliance and RoM increased with adaptation to aquatic locomotion, as expected, but this trend seems to have reversed somewhat in aquatic specialists. The IVJs of modern crocodylians had the greatest osteological RoM, but their morphometrics suggested reduced IVJ compliance, lending support to the idea that the trunks of early crocodylomorphs primarily were stabilized by their extensive osteodermal shields rather than IVJs. The most important structures for determining RoM and compliance of the trunk in Crocodylus were different in dorsoventral versus mediolateral bending, suggesting that changes in osteoderm and rib morphology over crocodylomorph evolution would have affected movements in some directions more than others.