TY  - JOUR
A1  - Strong, Catherine R. C.
A1  - Scherz, Mark D.
A1  - Caldwell, Michael Wayne
T1  - Deconstructing the Gestalt
BT  - new concepts and tests of homology, as exemplified by a re-conceptualization of "microstomy" in squamates
JF  - The anatomical record : AR ; advances in integrative anatomy and evolutionary biology ; an official publication of the American Association of Anatomists, AAA
N2  - Snakes-a subset of lizards-have traditionally been divided into two major groups based on feeding mechanics: "macrostomy," involving the ingestion of proportionally large prey items; and "microstomy," the lack of this ability. "Microstomy"-considered present in scolecophidian and early-diverging alethinophidian snakes-is generally viewed as a symplesiomorphy shared with non-snake lizards. However, this perspective of "microstomy" as plesiomorphic and morphologically homogenous fails to recognize the complexity of this condition and its evolution across "microstomatan" squamates. To challenge this problematic paradigm, we formalize a new framework for conceptualizing and testing the homology of overall character complexes, or "morphotypes," which underlies our re-assessment of "microstomy." Using micro-computed tomography (micro-CT) scans, we analyze the morphology of the jaws and suspensorium across purported "microstomatan" squamates (scolecophidians, early-diverging alethinophidians, and non-snake lizards) and demonstrate that key components of the jaw complex are not homologous at the level of primary character state identity across these taxa. Therefore, rather than treating "microstomy" as a uniform condition, we instead propose that non-snake lizards, early-diverging alethinophidians, anomalepidids, leptotyphlopids, and typhlopoids each exhibit a unique and nonhomologous jaw morphotype: "minimal-kinesis microstomy," "snout-shifting," "axle-brace maxillary raking," "mandibular raking," and "single-axle maxillary raking," respectively. The lack of synapomorphy among scolecophidians is inconsistent with the notion of scolecophidians representing an ancestral snake condition, and instead reflects a hypothesis of the independent evolution of fossoriality, miniaturization, and "microstomy" in each scolecophidian lineage. We ultimately emphasize that a rigorous approach to comparative anatomy is necessary in constructing evolutionary hypotheses that accurately reflect biological reality.
KW  - ancestral state reconstruction
KW  - functional morphology
KW  - homology
KW  - skull
KW  - anatomy
KW  - snake evolution
Y1  - 2021
U6  - https://doi.org/10.1002/ar.24630
SN  - 1932-8486
SN  - 1932-8494
VL  - 304
IS  - 10
SP  - 2303
EP  - 2351
PB  - Wiley
CY  - Hoboken
ER  -