Mioscalops, WILSON, 1960

Maguire, Kaitlin Clare & Schmitz, Joshua X. Samuels and Mark D., 2022, The fauna and chronostratigraphy of the middle Miocene Mascall type area, John Day Basin, Oregon, USA, PaleoBios 35, pp. 1-51 : 12-13

MIOSCALOPS WILSON, 1960

Mioscalops cf. ripafodiator HUTCHINSON, 1968 FIG. 5A , �

Referred specimens —From JDNM-4: right dentary fragment with partial m2 and m3, JODA 6414. From JDNM-226: left radius, JODA 15537.

Occurrence —JDNM-4, JDNM-226.

Description —The right dentary (JODA 6414, Fig. 5A ) includes the posterior portion of the ramus and the masseteric fossa, but lacks the ascending ramus and associated processes. The preserved portion of the dentary is relatively robust, with a depth of 2.43 mm at the anterior margin of the m3. The molars are well-worn, but clearly low-crowned. A distinct cingulum is present on the buccal surface of both molars, and the anterior margin of the m3. The m2 is missing most of the trigonid, with only the protolophid and posterior portions of the protoconid and metaconid remaining. In both the m2 and m3 the cristid obliqua joins the metalophid lingually, and the buccal reentrant valley is deep. Low, but distinct metastylids are present in both the m2 and m3, with a small notch separating them from the entoconid crest. The m2 talonid is worn flat, but the m3 talonid is basined and shows a well-developed hypolophid and entoconid crest. The m2 has a distinct entostylid (posterior accessory cuspid of Hutchinson 1968).

The radius (JODA 15537, Fig. 5B ) is incomplete, missing the capitular process and glenoid cavity from the proximal end. The approximate functional length of the radius is 6.88 mm. The distal end of the radius is ‘scalloped’ in medial view ( Fig. 5B ), as is typical of Scalopina (Hutchinson 1968).

Remarks —These are the only known specimens of Talpidae from the Mascall type deposits. Both the dentary and radius were collected in situ from the Mascall Tuff. While not reported previously from the Mascall Formation, talpids are common from other mid Miocene sites in Oregon ( Hutchison 1968). Hutchinson (1968) described five mole taxa from Barstovian sites in Oregon: Mystipterus pacificus , Mioscalops ripafodiator , Domninoides sp. , Scapanoscapter simplicidens , and Achlyoscapter longirostris . All of these taxa, with the exception of S. simplicidens , were found at Quartz Basin, while M. cf. ripafodiator , Domninoides sp. and S. simplicidens were found at the geographically and chronologically close Red Basin (Hutchinson 1968).

Though the Mascall material is insufficient for species identification, both the morphology and size of the dentary and radius are similar to described specimens of Mioscalops ( Ostrander 1986, Scalopoides of Wilson 1960, Hutchinson 1968, Gunnell et al. 2008). The teeth of JODA 6414 are relatively low-crowned, as in both Mystipterus Hall, 1930 and Mioscalops . As in Mioscalops , the protoconid and hypoconid of JODA 6414 are angular, there are distinct metastylids on the m2 and m3, and the cristid obliqua joins the metaconid relatively lingually ( Wilson 1960, Hutchinson 1968). The metastylid and entoconid crest are present, and close the talonid lingually, as in both Mystipterus and Mioscalops , but the metastylid of JODA 6414 is relatively prominent as in Mioscalops . The preserved portion of the dentary is relatively robust, like that of the Barstovian Mioscalops ripafodiator (Hutchinson 1968) .

Features of the dentition also rule out the other taxa previously described from the Barstovian of Oregon (Hutchinson 1968). In Domninoides Green, 1956 , the cristid obliqua joins the metastylid rather than the metaconid, and the talonid is open lingually (Hutchinson 1968), unlike JODA 6414. The trigonid of JODA 6414 is not anteroposteriorly compressed, as it is in Scapanoscapter (Hutchinson 1968, Gunnell et al. 2008). Unlike JODA 6414, in Achyloscapter there is no metastylid and the cristid obliqua joins the protolophid buccal to the metaconid (Hutchinson 1968, Gunnell et al. 2008).

The radius (JODA15537) is relatively robust compared to that of shrew-moles ( Urotrichini ), but relatively elongate and gracile compared to those of Domninoides and living Scalopini ( Hutchison 1968, Freeman 1979). The radius is overall quite similar to described specimens of Mioscalops , suggesting a mole that was less specialization for burrowing than Domninoides and Scapanoscapter , as well as more recent Scalopini ( Hutchison 1968) .

Figures

Figure 5. Mioscalops cf. ripafodiator. A. Right dentary fragment with partial m2 and m3, JODA 6414. B. Radius, JODA 15537. Scale bar=1 mm.