Forelimb myology and the evolutionary relationships of the aardvark, Orycteropus afer, and other small afrotheres

Orycteropus;Afrotheria;forelimb myology;mammals;Anatomy

Voegele, Georgina McKusickRose, Kenneth D. ;

Johns Hopkins University

关键词: Orycteropus;    Afrotheria;    forelimb myology;    mammals;    Anatomy;   

Others  :  https://jscholarship.library.jhu.edu/bitstream/handle/1774.2/37172/VOEGELE-DISSERTATION-2014.pdf?sequence=1&isAllowed=y

瑞士|英语

来源: JOHNS HOPKINS DSpace Repository

【 摘 要 】

The aardvark, Orycteropus afer, is the sole surviving member of the order Tubulidentata, and it has such unusual morphology that few skeletal or dental characters link it to other living mammals.Instead researchers compare the skeleton of Orycteropus with bones from extinct primitive ungulates, the condylarths.Recent genetic research places Orycteropus in Afrotheria, a grouping of mammals that conflicts with conventional mammalian systematics based on morphology and finds little support from fossil evidence (Stanhope et al., 1998).Thus the evolutionary relationships of Orycteropus are highly controversial.This dissertation utilizes detailed dissection-based information about the forelimb myology of the aardvark and other small afrotheres, and similar information available in the literature for most other mammals, to bolster the morphological evidence for the position of the aardvark within Eutheria.The dissected mammals were the afrotheres Orycteropus afer, Potamogale velox, Microgale dobsoni, Calcochloris leucorhinus (described for the first time), Rhynchocyon cirnei, Elephantulus brachyrhynchus, Petrodromus tetradactylus, Procavia capensis, Heterohyrax brucei, and artiodactyls Pecari tajacu, and Tragulus napu for comparison.A total of 60 characters were identified and scored for 46 orders or families of mammals, and the program Mesquite 2.75 used for a parsimony analysis.The 50% majority rules consensus tree of 178 trees indicates that forelimb myology places Orycteropus as basal within eutherian mammals along with Tenrecidae and Macroscelididae rather than with the paenungulates and ungulates.The forelimb myology characters, particularly features of the flexor muscles of the forearm and the muscles of the manus, indicate that Orycteropus is most closely related to Chrysochloridae and Tenrecidae (Afrosoricida) with Macroscelididae as the sister group to this clade, together comprising Afroinsectiphilia.Xenarthra are clearly unrelated to Orycteropus, but also retain many primitive features.The forelimb myology of the ungulates is quite derived in comparison with Orycteropus; Paenungulata do share many similarities with the ungulates, however, but still retain some primitive features in common with Orycteropus.In addition to myological features linking Orycteropus with the Afrosoricida, some possible myological synapomorphies for Afrotheria are identified, notably an unusual muscle identified here as m. cubitalis.This indicates there may be morphological support for Afrotheria in the myology.