Parascalops grayensis, Oberg & Samuels, 2022

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 : 10-14

Parascalops grayensis sp. nov.

Figure 5A – F and Figure 6A - J

zoobank.org/ 942FCF9D-D9FD-4A70-9B12-D09C1DCE5476

Type material. ETMNH 6939 - left humerus.

Paratypes. ETMNH 6940 - right humerus ; ETMNH 12305 - left humerus ; ETMNH 20736 - right humerus ; ETMNH 20782 - right humerus ; ETMNH 14849 - left radius ; ETMNH 20739 - right ulna ; ETMNH 20754 - right ulna, missing distal end and olecranon process ; ETMNH 20748 - nearly complete disarticulated left manus with six carpals (scaphoid, lunar, capitate, trapezium, triquetrum, and ulnar sesamoid?), three metacarpals ( III, IV, and V), four proximal phalanges (I, III, IV, V), four medial phalanges ( II-V), five terminal phalanges (I- V), and a partial right manus with three carpals (capitate, trapezium, and ulnar sesamoid?) ; ETMNH 24662 left M3 .

Type locality. Gray Fossil Site, TN, USA.

Etymology. Species named for the locality where it was discovered.

Diagnosis. Entepicondylar foramen of the humerus is small and laterally positioned; pectoral tubercle is a large ridge, centrally positioned and extends almost half of entire diaphysis length; pectoral tubercle is robust; capitulum is smaller and angled 20-30 degrees superiorly; ulna and radius are large and robust.

Description. The humerus is longer than broad ( Figure 5A - B ; Table 4). The greater tuberosity is large and pronounced. There is a thin separation between the greater tuberosity and the humeral head. The brachialis fossa is triangular in shape. The teres tubercle is relatively large and curved proximally. There is a large gap between the entepicondylar process and the teres tubercle. The capitulum is parallel with the trochlea. The trochlea

PALAEO- ELECTRONICA.ORG touches the fossa of the M. flexor digitorum ligament. The pectoral tubercle is positioned proximally and can be either a large oval tubercle (ETMNH 6940, 12305, 14849) or a thin ridge (ETMNH 6939, 20736, and 20782). The scalopine ridge is weakly developed, and visible in several specimens (ETMNH 6939, 20736, and 20782).

In the radius (ETMNH 14849, Figure 5C ), the capitular head is mediolaterally broad with a flat, square edge. The lunar articular facet is quite large, has a curved edge, and somewhat deep. The M. abductor pollicis tendon groove is at a sharp angle. The distal end is large and flares mediolaterally. There is a clean break through the center of the diaphysis that was repaired. There is no evidence of healing on this break suggesting it occurred post-burial. The distal end of the radius is relatively swollen.

The ulnae are short, mostly straight, and very robust ( Figure 5D - F ). The proximal olecranon crest forms a sharp angle with the shaft and a large blade greatly separated from the semilunar notch. The abductor fossa is enlarged. The semilunar notch is very well defined (appears as a strong semicircle). There is a large and curved medial olecranon crest. The triceps scar is large and relatively wide. The abductor scar is elongate and makes up part of the base of the lateral olecranon crest. The distal end and the olecranon process are missing from ETMNH 20754.

There is one nearly complete manus (ETMNH 20748, Figure 6–A - I ). All elements are completely disarticulated. There are eight carpals, five metacarpals, nine proximal and medial phalanges, and five terminal phalanges. All manus elements are large and robust. The carpals are blocky and large. The metacarpals and phalanges are short, anteroposteriorly compressed and mediolaterally broad. The terminal phalanges are elongate, broad, and bifurcated by large nutrient foramina.

There is one tooth referred to this taxon, a left M3 (ETMNH 24662, Figure 6J ). The lingual portion of the M3 has a large and prominent parastyle, a prominent and well-worn paracone that is connected via a continuous mesostyle to the distinctly smaller metacone. The labial portion of the tooth is dominated by a large protocone, which as a consequence of wear is fused to relatively small protoconule and metaconule. The M3 length is 1.72 mm and width is 1.86 mm.

Discussion. Osteological characters that distinguish Parascalops breweri (Hairy-tailed mole) from all other known talpids include: the trochlea touches the fossa of the M. flexor digitorum ligament (Skoczeń, 1993), the brachialis fossa has a triangular shape (Hutchison, 1968), the fissure separating the greater tuberosity from the head is thin and subtle, the teres tubercle is about onethird the size of the pectoral ridge and has a strong curve, the scalopine ridge is weak and fragmentary with a prominence at about half of its length (Skoczeń, 1993), the position of the pectoral tubercle is proximal, the groove for the tendon of M. abductor pollicis longus on the radius is angled sharply, the top of the capitular process of the radius is square-shaped and flat, the medial olecranon crest of the ulna is more medial and has a strong medial curve, and the brachialis scar on the ulna is straight and thin. These characters are present on the GFS material, but morphology and size ( Table 4) differences distinguish it from the extant species Parascalops breweri .

There are two described species within the genus Parascalops : P. breweri (extant) and P. fossilis from the Pliocene of Poland (Skoczeń, 1993). They are very similar in morphology but have some important differences. The characters differentiating P. fossilis from P. breweri are: 1) a significantly smaller humerus, 2) shallower fossa brachialis, 3) more oblique lesser tuberosity that passes the edge of the pectoral crest at a low angle that extends beyond the border of the humeral shaft, and 4) the medial vascular foramen on the diaphysis is larger (Skoczeń, 1993). The GFS material does not exhibit any of these morphological features.

The single tooth referred to Parascalops grayensis sp. nov., a left M3 (ETMNH 24662), is quite similar to studied specimens of P. breweri . The parastyle of the GFS specimen is larger than that of studied specimens of the extant P. breweri . Also, the angle between the parastyle, paracone, and mesostyle is more open in the GFS specimen than the extant species. Due to the lack of described dental material of P. fossilis , the GFS specimen could not be compared to that taxon.

Parascalops grayensis sp. nov. is similar in size ( Table 5) and general morphology to P. breweri , but there are a few distinct differences. Evaluating the humerus of Parascalops grayensis sp. nov., the entepicondylar foramen is smaller and more laterally positioned on the diaphysis, the pectoral tubercle is a large, robust ridge, centrally positioned and almost half of entire diaphysis length, and the capitulum is smaller and angled 20-30 degrees superiorly from the ectepicondylar process. Parascalops breweri humeri typically have a large entepicondylar foramen that is more medially positioned, the pectoral tubercle is a prominent lump on the diaphysis, not a ridge, and the capitulum is relatively large and angled parallel to the ectepicondylar process. The ulnae and radii of P. grayensis sp. nov. are larger and more robust ( Table 4). Muscle scars on these elements are more pronounced and have more rugose texture. The distal ends of these elements also appear more swollen than those of P. breweri .

Parascalops grayensis sp. nov. can be differentiated from Parascalops fossilis by size ( Table 5) and general morphology. The humerus of Parascalops grayensis sp. nov. is large, the fossa brachialis is deep, the greater tuberosity is longer and more robust, the pectoral tubercle is large, robust and forms a ridge, and the entepicondylar foramen is small and laterally positioned. Parascalops fossilis has a shallow fossa brachialis, a smaller, less robust greater tuberosity, a small (almost non-existent) pectoral tubercle, and a relatively large, medially positioned entepicondylar foramen.

Parascalops grayensis sp. nov. is morphologically similar to, and falls within the biogeographic range of, extant P. breweri . This taxon may be ancestral to the extant species. These fossils represent the first pre-Pleistocene record of the genus in North America and earliest record globally. This extends the known fossil history for the genus by 4 million years in North America.

Figures

FIGURE 5. Parascalops grayensis sp. nov. material. ETMNH 6939, left humerus - A) posterior and B) anterior views. ETMNH 14849, right radius - C) medial view. ETMNH 20748, right ulna - D) medial, E) anterior, and F) lateral views.

FIGURE 6. Parascalops grayensis sp. nov. material. ETMNH 20748, nearly complete disarticulated manus parts in dorsal view, A) articulated phalanges with claw cores (digits V - I), B) right trapezium, C) right capitate, D) right ulnar sesamoid, E) left scaphoid, F) left lunar, G) left triquetrum, H) left capitate, and I) left trapezium. ETMNH 24662, left M3 - J) occlusal view. Scale bars equal 1 mm.