Evolutionary assembly and disassembly of the mammalian sternum

Brent, Ava E.; Buchholtz, Emily A.; Mansfield, Jennifer H.

doi:10.1016/j.cub.2022.11.055

Cited by 3 publications

(2 citation statements)

References 58 publications

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“…In such a scenario, the “clavicular deltoid” probably appeared around the origin of Cynodontia, although maximum likelihood ASR suggests a later origin (Supporting Information Appendix S4). The loss of a distinct interclavicle as it was incorporated into the sternal complex in stem therians (Bendel et al, 2022; Brent et al, 2023) probably coincided with a restriction of the origin of the “clavicular deltoid” to the clavicle only (state 2), as observed in extant Theria.…”

Section: Resultsmentioning

confidence: 97%

“…Major changes occurring within nonmammalian cynodonts principally revolve around the transformation of deltoid and supracoracoid musculature, affecting the structure of the scapula (characters 5, 6, 21, 22) and humerus (characters 7, 23–25), in addition to the appearance of a novel muscle, the TMA (character 4). Changes occurring within Theriiformes are related to the reduction or loss of the interclavicle (at least as a large, discrete element; Bendel et al, 2022; Brent et al, 2023) and clavicle, and diminishment of the coracoid plate to form the coracoid process of the glenoid, which modified the origins of the DCl, PECT, BICB, CBB and CBL (characters 9, 10, 31, 26, 27). Other changes possibly include modification of forearm musculature (characters 50, 51, 59, 73), but the scarcity of osteological correlates distal to the elbow warrants caution in this assessment.…”

Section: Discussionmentioning

confidence: 99%

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The fossil record of appendicular muscle evolution in Synapsida on the line to mammals: Part I—Forelimb

Bishop,

Pierce

2023

The Anatomical Record

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This paper is the first in a two‐part series that charts the evolution of appendicular musculature along the mammalian stem lineage, drawing upon the exceptional fossil record of extinct synapsids. Here, attention is focused on muscles of the forelimb. Understanding forelimb muscular anatomy in extinct synapsids, and how this changed on the line to mammals, can provide important perspective for interpreting skeletal and functional evolution in this lineage, and how the diversity of forelimb functions in extant mammals arose. This study surveyed the osteological evidence for muscular attachments in extinct mammalian and nonmammalian synapsids, two extinct amniote outgroups, and a large selection of extant mammals, saurians, and salamanders. Observations were integrated into an explicit phylogenetic framework, comprising 73 character–state complexes covering all muscles crossing the shoulder, elbow, and wrist joints. These were coded for 33 operational taxonomic units spanning >330 Ma of tetrapod evolution, and ancestral state reconstruction was used to evaluate the sequence of muscular evolution along the stem lineage from Amniota to Theria. In addition to producing a comprehensive documentation of osteological evidence for muscle attachments in extinct synapsids, this work has clarified homology hypotheses across disparate taxa and helped resolve competing hypotheses of muscular anatomy in extinct species. The evolutionary history of mammalian forelimb musculature was a complex and nonlinear narrative, punctuated by multiple instances of convergence and concentrated phases of anatomical transformation. More broadly, this study highlights the great insight that a fossil‐based perspective can provide for understanding the assembly of novel body plans.

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Section: Resultsmentioning

confidence: 97%

Section: Discussionmentioning

confidence: 99%

The fossil record of appendicular muscle evolution in Synapsida on the line to mammals: Part I—Forelimb

Bishop,

Pierce

2023

The Anatomical Record

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In search of the origin of crown Mysticeti

Tsai

2023

Journal of the Royal Society of New Zealand

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The sternum and interclavicle of Aelurognathus tigriceps (Broom & Haughton, 1913) (Therapsida: Gorgonopsia), with comments on sternal evolution in therapsids

SIDOR,

MANN

2024

Comptes Rendus Palevol

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Understanding the origin and evolution of the unique mammalian respiratory system hinges on our knowledge of the osteological changes in the pectoral apparatus (i.e., scapulocoracoid, cleithrum, clavicle, interclavicle, sternum) throughout the synapsid fossil record. Among non-mammalian therapsids, documentation of this anatomy is woefully incomplete, with groups such as dinocephalians and gorgonopsians remaining poorly documented. Here we provide a detailed anatomical description of an articulated sternum and interclavicle of a well-preserved specimen of Aelurognathus tigriceps (Broom & Haughton, 1913) from the Lopingian upper Madumabisa Mudstone Formation, Luangwa Basin of Zambia. The sternal morphology reveals new anatomical details on the attachment sites for the ribs, showing three distinct facets, and a previously undescribed depression on the ventral surface for the attachment of the interclavicle. We also provide a preliminary discussion of the morphological variation of these elements both within Gorgonopsia and across Therapsida.

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Evolutionary assembly and disassembly of the mammalian sternum

Cited by 3 publications

References 58 publications

The fossil record of appendicular muscle evolution in Synapsida on the line to mammals: Part I—Forelimb

The fossil record of appendicular muscle evolution in Synapsida on the line to mammals: Part I—Forelimb

In search of the origin of crown Mysticeti

The sternum and interclavicle of Aelurognathus tigriceps (Broom & Haughton, 1913) (Therapsida: Gorgonopsia), with comments on sternal evolution in therapsids

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