Association of Elements
Based on comparative anatomy and size, mandibles (discussed in more detail in the specific diagnoses), and femora can be divided into two morphotypes, humeri into three.
A distribution of length in all measured Langebaanweg humeri exhibits a clear break at 14 mm (Figure 1), with the majority (65 of 70 measured specimens) below this amount. Among these smaller humeri, there is another gap between those showing a length/distal width ratio near 1.39 (43 individuals) and those with one near 1.21 (22 individuals; see
Figure 2). The five large humeri also show a length/distal width ratio of 1.39 (Figure 2). The only extant chrysochlorids we observed to approach the most common humeral dimensions among the Langebaanweg material are Eremitalpa and Chrysospalax, both of which have a relatively narrow distal humeral margin (for a chrysochlorid). The former overlaps slightly with the smaller size range of the most common humeral morphotype at Langebaanweg, whereas Chrysospalax is substantially larger than any of the fossil golden moles described here (see
Discussion). If our assumption is correct that relative abundance is an accurate guide to the association of the most common mandibular and humeral morphotypes at Langebaanweg, then the ratio of dentary/humerus length resembles that of Eremitalpa, as does the ratio of humerus length/distal width of this new species (Table 1). Craniodentally, however, this taxon shows many differences and is clearly distinct from Eremitalpa, and more closely resembles Chrysochloris asiatica (see species diagnosis, below).
Femora show size variation indicative of multiple species (Table 1). Based on comparisons with extant species, some femora and the few preserved scapular fragments represent individuals larger than those represented by the most common dentaries and humeri at Langebaanweg, and cannot confidently be associated with any craniodental remains. We therefore do not assign these elements to any novel species. Five of the measured femora show an average length of 15.6 mm (Figure 3), similar to that of extant Amblysomus hottentotus. All of the other femora are below 14 mm in length, averaging 12.9 mm, statistically indistinguishable from C. asiatica and Neamblysomus julianae. Femora have a round, globular condyle proximally and a scar for the fovea capitis interrupting the articular surface of the femoral head from its midpoint to the femoral neck. Greater and lesser trochanters are present, but small, and without any concavity for attachment of obturator musculature. A third trochanter is situated near the midpoint of the shaft. A shallow articular surface for the patella marks the distal femoral margin. The femoral condyles are slightly displaced medially, reflecting the presence of a flange for muscle attachments on the lateral margin of the distal femur.
Intact scapulae are lacking. However, several fragments exist with a diagnostically chrysochlorid glenoid region and scapular spine that extends far lateral to the glenoid articular surface (Figure 3). In the two specimens with at least a partially intact distal spine (SAM-PQL 35122, 35106), the metacromion process is narrow and elongate, pointing caudally away from the glenoid. These appear to be proportional in size to the larger morphotype represented by a small number of humeri and femora.
Here, we name two new chrysochlorid species using the most diagnostic elements of their skeletons as types. Furthermore, we add to the referred specimens of the two new species those elements that, based on relative abundance and proportions among living chrysochlorids, match those of our proposed type specimens. In addition, given our proposed species limits, coefficients of variation (the standard deviation expressed as a percentage of the mean) for dentary and humerus lengths are under 5 and comparable to those for modern taxa (Table 1). We leave unnamed a third Langebaanweg chrysochlorid morphotype, represented by relatively large humeri, femora, and scapular fragments, which cannot yet be associated with any craniodental remains.