Received Jul 28; Accepted Dec 6. This is an open access article distributed under the terms of the Creative Commons Attribution License , which permits unrestricted use, distribution, reproduction and adaptation in any medium and for any purpose provided that it is properly attributed. This article has been cited by other articles in PMC.
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Abstract Non-mammaliaform cynodonts gave rise to mammals but the reproductive biology of this extinct group is still poorly known. Introduction Intraspecific aggregations, consisting of multiple individuals interacting with each other, have been documented across many tetrapod orders. Open in a separate window. Figure 1.
Table 1 Range in basal skull length mm for each ontogenetic stage of Galesaurus and Thrinaxodon. Table 2 Characteristics of Galesaurus planiceps and Thrinaxodon liorhinus individuals found within intraspecific groups. See text for institutional abbreviations. See also Table 1. Therefore, it is equivocal whether this specimen is associated with the other three individuals. Details of specimen taken from Brink Table 3 Postcranial measurements in mm of Galesaurus planiceps and Thrinaxodon liorhinus. Abbreviations BSL basal skull length hum humerus isch ischium rad radius scap scapula — indicates the skeletal element was either missing, broken, or not measured.
Figure 2. Figure 3. Figure 4. Figure 5. Figure 6. Figure 7. Associated late juvenile specimens of Thrinaxodon liorhinus. Figure 8. Figure 9. Specimen TM Block TM , collected from Harrismith, contains two articulated skeletons of Thrinaxodon that are lying beside each other in a dorsal-up orientation Fig.
Figure Discussion Summary of aggregations and skeletal representation in basal cynodonts Our comprehensive survey found nine unequivocal cases in which individuals of either Galesaurus planiceps or Thrinaxodon liorhinus were preserved together Table 2. The first possibility is ruled out with the following taphonomic evidence: 1.
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Table 4 Ratios of limb bone measurements for specimens of Galesaurus planiceps and Thrinaxodon liorhinus listed in Table 3. Immature includes juvenile and subadult individuals. See text for further details. Aggregations in other non-mammalian synapsids Aggregations among other non-mammalian synapsids are relatively rare, with only a few examples of aggregations found in a basal synapsid, three dicynodont taxa, and at least one eucynodont. Abbreviation BSL Basal skull length. Aggregations in modern amniotes Extant squamates can form seasonal aggregations, including mating and winter aggregations e.
Size of young The juveniles in the two basal cynodont aggregations that represent parental care Figs. Conclusions A thorough survey of two basal non-mammaliaform cynodonts revealed several instances of aggregations in Thrinaxodon liorhinus but only two aggregations in Galesaurus planiceps Table 2.
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Supplemental Information Table S1 Full list of Galesaurus planiceps and Thrinaxodon liorhinus specimens observed in this study. Click here for additional data file. Additional Information and Declarations Competing Interests The authors declare there are no competing interests.
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