What are the most accurate categories for mammal tarsus arrangement? A review with attention to South American Notoungulata and Litopterna.

What are the most accurate categories for mammal tarsus arrangement? A review with attention to South American Notoungulata and Litopterna.
J Anat. 2019 Aug 02;:
Authors: Lorente M
Abstract
The arrangement of the tarsus has been used to differentiate afrotherian and laurasiatherian ungulates for more than a century, and it is often present in morphological matrices that include appendicular features. Traditionally, it has two states: (i) an alternating tarsus, where proximal elements are interlocked with central and distal elements positioned like the bricks of a wall; and (ii) a serial tarsus, where elements are not interlocked. Over the years, these states became synonymous with the presence or absence of an astragalocuboid contact. Within the South American order Notoungulata, a third disposition was recognized: the reversed alternating tarsus, associated with a calcaneonavicular contact. This state was considered to be a synapomorphy of 'advanced' Toxodontia families (Notohippidae, Leontiniidae and Toxodontidae), but a further inspection of its distribution shows that it occurs throughout Mammalia. Additionally, it overlaps the serial tarsus condition as originally defined, and it probably has no functional or phylogenetic significance. Calcaneonavicular and astragalocuboid contacts are non-exclusive, and their presence within a species, genus or family is not constant. Serial and alternating imply movements of the articulations ...

Source: Journal of Anatomy - August 1, 2019 Category: Anatomy Authors: Lorente M Tags: J Anat Source Type: research