首页|The Late Cretaceous eutherian Zalambdalestes reveals unique axis and complex evolution of the mammalian neck

The Late Cretaceous eutherian Zalambdalestes reveals unique axis and complex evolution of the mammalian neck

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The typical mammalian neck consisting of seven cervical vertebrae(C1-C7)was established by the Late Permian in the cynodont forerunners of modern mammals.This structure is precisely adapted to facilitate movements of the head during feeding,locomotion,predator evasion,and social interactions.Eutheria,the clade including crown placentals,has a fossil record extending back more than 125 million years revealing significant morphological diversification in the Mesozoic.Yet very little is known concerning the early evolution of eutherian cervical morphology and its functional adaptations.A specimen of Zalambdalestes lechei from the Late Cretaceous of Mongolia boasts exceptional preservation of an almost complete series of cervical vertebrae(C2-C7)revealing a highly modified axis(C2).The significance of this cervical morphology is explored utilizing an integrated approach combining comparative anatomical examination across mammals,muscle reconstruction,geometric morphometrics and virtual range of motion analysis.We compared the shape of the axis in Zalambdalestes to a dataset of 88 mammalian spe-cies(monotremes,marsupials,and placentals)using three-dimensional landmark analysis.The results indicate that the unique axis morphology of Zalambdalestes has no close analog among living mammals.Virtual range of motion analysis of the neck strongly implies Zalambdalestes was capable of exerting very forceful head movements and had a high degree of ventral flexion for an animal its size.These findings reveal unexpected complexity in the early evolution of the eutherian cervical morphology and suggest a feeding behavior similar to insectivores specialized in vermivory and defensive behaviors in Zalambdalestes akin to modern spiniferous mammals.

AtlasAxisVertebral columnStem placentalMorphologyPaleoecology

Patrick Arnold、Katarzyna Janiszewska、Qian Li、Jingmai K.O'Connor、?ucja Fostowicz-Frelik

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Institute of Biochemistry and Biology,University of Potsdam,Potsdam D-14476,Germany

Environmental Paleobiology Department,Institute of Paleobiology,Polish Academy of Sciences,Warsaw 00-818,Poland

Key Laboratory of Evolutionary Systematics of Vertebrates,Institute of Vertebrate Paleontology and Paleoanthropology,Chinese Academy of Sciences,Beijing 100044,China

The Field Museum of Natural History,Chicago IL 60605,USA

Department of Organismal Biology and Anatomy,The University of Chicago,Chicago IL 60637,USA

Evolutionary Paleobiology Department,Institute of Paleobiology,Polish Academy of Sciences,Warsaw 00-818,Poland

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National Science Centre(NCN,Kraków,Poland)Polish National Agency for Academic Exchange(NAWA,Warszawa,Poland)

2015/18/E/NZ8/00637BPN/BEK/2021/1/00357/U/00001

2024

10.1016/j.scib.2024.04.027

科学通报(英文版)
中国科学院

科学通报(英文版)

CSTPCD
ISSN：1001-6538
年,卷(期)：2024.69(11)