Mioscalops sp.

Oberg, Danielle E. & Samuels, Joshua X., 2022, Fossil moles from the Gray Fossil Site (Tennessee): Implications for diversification and evolution of North American Talpidae, Palaeontologia Electronica (a 33) 25 (3), pp. 1-39 : 14-16

Mioscalops sp. Ostrander et al., 1986

Figure 7A - C

1960 Scalpoides; Wilson, p. 43, fig. 34-39, 42-46

1968 Scalopoides ; Hutchinson, p. 58-80

1968 Mioscalops ; Ostrander; Mebrate; Wilson,

p. 9

2000 Wilsonius ; Kretzoi and Kretzoi, p. 427

Type. Mioscalops isodens , left lower haw with i3- p1, p4-m2, No. 10067, University of Kansas

Museum of Natural History, Pawnee Creek Formation, late Arikareean NALMA.

Referred specimens. ETMNH 6941 - left humerus; ETMNH 6942 - left humerus; ETMNH 6943 - left humerus, distal end; ETMNH 9565 - right humerus, distal end; ETMNH 10345 - left humerus, distal end; ETMNH 16024 - right humerus; ETMNH 20738 right ulna; ETMNH 20740 - right humerus; ETMNH 20743 - left humerus, distal end; ETMNH 20744 - right humerus; ETMNH 20745 - right humerus, distal end; ETMNH 20971, right humerus.

Locality. Gray Fossil Site, TN, USA.

Description. The humeri of this genus have a long, gracile diaphysis with ends that do not flare as mediolaterally ( Table 6) as in extremely fossorial moles. In the posterior view of the humerus ( Figure 7A ), the ectepicondylar and entepicondylar processes are angled sharply. The entepicondylar process is more robust than the ectepicondylar process. The ectepicondylar process projects laterally at a higher angle. The trochlea is mediolaterally elongated. The bicipital groove is angled medially. The teres tubercle is connected to the greater tuberosity via a thin ridge, which has a welldefined and relatively large bicipital groove. The humeral head is relatively large when compared to other talpid taxa. The radial notch is a little depressed. The olecranon fossa is small and has an oval/teardrop shape. The capitulum is saddle shaped (convex inferiorly, concave superiorly). The entepicondylar foramen is large and oval.

In the anterior view ( Figure 7B ), the humerus has a long shaft, with relatively narrow ends, a saddle shaped capitulum, and small entepicondylar foramen. The position of the entepicondylar foramen is much closer to the medial aspect of the distal end. The pectoral tubercle can vary in shape from a tubercle (ETMNH 6943, 9565, 10345, 20740, 20744, and 20745) to a small ridge (ETMNH 6941, 6942, 16024, 20743, and 20971). The greater tuberosity is massive and not separated from the lesser tuberosity. The pectoral crest starts at the greater tuberosity and stops 2/3 of the way down the diaphysis. The pectoral ridge con-

PALAEO- ELECTRONICA.ORG ceals most of the teres tubercle in the anterior view. There are small foraminae on either side of the pectoral ridge, near the base of the pectoral tubercle.

The ulna is almost complete, except that the olecranon process is broken off ( Figure 7C ). The distal end flares quite a bit. This ulna is very robust despite being so small. The diaphysis is long, relatively gracil, and mildly sinusoidal. There are no visible muscle scars along the diaphysis. Around the semilunar notch, the processus anconeus greatly overhangs the notch, but the coronoid process is quite pronounced as in more fossorial talpids. This trait is not common in semi-fossorial talpids.

Discussion. Mioscalops is the correct name to use when describing Scalopoides Wilson 1960 . Scalopoides Wilson 1960 , a common Miocene mole, is a junior homonym of Scalopoides Bode 1953 , a coleopteran from the Upper Lias of Europe. Therefore, the new name Mioscalops Ostrander et al. 1986 replaced Scalopoides Wilson 1960 . Another genus, Wilsonius Kretzoi and Kretzoi 2000 , was erected in Europe to describe the same Miocene talpid material; however, this genus is considered synonymous with Mioscalops Ostrander et al. 1986 . Therefore, any talpid material being classified at the generic or species level as Scalopoides Wilson 1960 or Wilsonius Kretzoi and Kretzoi 2000 , should be assigned to Mioscalops Ostrander et al., 1968 .

Mioscalops has always been placed in the Scalopini tribe, but with little justification. Scalopini talpids are united by the presence of a scalopine ridge ( Campbell, 1939); however, this “ridge” is actually a scar that runs parallel to the greater tuberosity on the diaphysis in the posterior view of the humerus (Hutchison, 1968). This character is also present in other tribes such as the Talpini , Urotrichini (Rzebik-Kowalska, 2014) , and Scaptonychini (Skoczeń, 1980) ; therefore, it is not a reliable synapomorphy for the tribe Scalopini . Instead, researchers now rely on differences in dental characteristics to separate Scalopini talpids from other talpids (see Schwermann et al., 2019, S1 for a discussion of the dental formula). Recent geometric morphometric and phylogenetic analyses (e.g., Schwermann et al., 2019) have also placed Mioscalops within the Scalopini tribe, thus we do the same.

Mioscalops is most morphologically similar to Scapanus , Condylura , and Scapanulus . Mioscalops and Scapanus (Western North American moles) both have humeral heads that are in line with the diaphysis, the clavicular articular facet is semi-oval, a small teres tubercle, and a prominent scalopine ridge (Hutchison, 1968); however, the genus Scapanus includes three species of very robust scalopine talpids, and all documented fossil forms are similarly robust (Hutchison, 1968, 1974, 1987). GFS Mioscalops is not nearly robust enough to be considered Scapanus .

Mioscalops also shares similarities with Condylura cristata (star-nosed mole) in the proportions of the articular ends, the relative size of the teres tubercle, the shape of the humeral head, and the degree of overall robustness, but there are more differences between Condylura and Mioscalops than there are similarities. Some differences include: the direction of the humeral head, lack of scalopine ridge, clavicular articular facet being parallel to humerus long axis, strong separation from humeral head from clavicular facet, and a narrower trochlea in Condylura (Hutchison, 1968, 1984).

Mioscalops is morphologically similar to Scapanulus oweni (Gansu mole). They have similar humeral head orientations and sizes, a scalopine ridge, a broad trochlea, an absent channel separating the humeral head from the greater tuberosity, and the proximal end of the #llustrat tunnel is anteriorly visible (Hutchison, 1968). Differences in teres tubercle shape and size, as well as the size of the pectoral crest, differentiate Mioscalops from Scapanulus .

The name Mioscalops has commonly used as a “garbage-bin” taxon for any talpid found during the Miocene, but it is morphologically distinct from other Neogene talpid taxa. Mioscalops is known from the Oligo-Miocene through the Pliocene of North America and the Miocene of Europe ( Gunnell et al., 2008). Mioscalops was widely distributed across North America making it the most common talpid to find in a Cenozoic fossil locality that contains talpids ( Gunnell et al., 2008).

Figures

FIGURE 7. Mioscalops sp. skeletal material. ETMNH 6942, left humerus - A) posterior and B) anterior views. ETMNH 20738, right ulna - C) medial view. Scale bar equal 1 mm.