Rosendo pascuali ( Simpson, 1967 )
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https://doi.org/ 10.1206/3903.1 |
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persistent identifier |
https://treatment.plazi.org/id/03F087CC-FF99-381E-FE28-FC66ECA3F930 |
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Carolina |
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scientific name |
Rosendo pascuali ( Simpson, 1967 ) |
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Rosendo pascuali ( Simpson, 1967)
Figure 3 View FIGURE 3
HOLOTYPE: AMNH FM 29405 , maxillary fragment with left P2–M2.
TYPE LOCALITY: Collected at the Gran Barranca in 1930. Simpson (1967: 185) recorded its provenance as: “On line of section M in Simpson field book for 1930 in the American Museum of Natural History, level marked on section just below the erosional base of upper channel bed.” In current stratigraphic terminology, the holotype derives from the uppermost levels of the Puesto Almendra (PA) Member of the Sarmiento Formation (Gelfo et al., 2009). López et al. (2010) referred specimens from La Cancha (Gran Barranca) to this species (“ E? pascuali ”). Presuming that this is the same faunal level as the one described by Simpson, it occurs within the Vera Member, which is interposed between the Lower PA and Upper PA members (see Bellosi, 2010).
AGE: Although Simpson (1967) regarded the holotype as Mustersan in age, his careful attention to stratigraphic detail indicates that the holotype was collected higher than the levels producing the typifying assemblage of the Mustersan SALMA. As mentioned, the uppermost levels of the Puesto Almendra Member of the Sarmiento Formation are now recognized as producing the distinctive ‘‘Astraponotéen plus supérieur’’ ( APS) fauna, which pertains to the Tinguirirican SALMA ( Wyss et al., 1994; Bond et al., 1996; Flynn et al., 2003; Gelfo et al., 2009).
REFERRED SPECIMENS: AMNH FM 29474, right mandible with i3–m3. SGOPV 3051, left mandible with p3–m1 plus erupting m2. SGOPV 3096, isolated left m3. SGOPV 2991, fragmentary right maxilla preserving P2 through the anterior half of M1 and slivers of an erupting M3.
DIAGNOSIS (emended from Simpson, 1967): Among notohippids of similar age, slightly smaller than specimens currently referred to E. obscurus and E. bondi , and substantially larger than E. neilopdykei . Less hypsodont than all species of Eomorphippus . Unusual among all notoungulates, first lower premolar (either p1 or dp1) either replaced late in ontogeny, after m3 erupts and is well worn, or dp1 erupts unusually late.
DESCRIPTION: Rosendo pascuali , identified as “‘ Eomorphippus ’ cf. pascuali ” by Wyss et al. (1994) and as “‘ Eomorphippus ’ sp. cf. ‘ E. ’ pascuali ” by Flynn et al. (2003), is currently known from upper and lower teeth as well as from both sides of the modern Andean divide. R. pascuali represents the smaller bodied of the two low-crowned notohippids described in this study. The two AMNH specimens listed in Referred Specimens are of particular relevance here. “? E. pascuali ” was authored by Simpson (1967) on the basis of a maxilla (AMNH FM 29405) and a doubtfully referred mandible (AMNH FM 29474), both collected from the same locality (high in the Mustersan-aged section) that produced a specimen of E. obscurus, AMNH FM 29462 (see above). Discovery of the new material described here from Chile further underscores the distinctiveness of previously recognized material of “? E. pascuali ” relative to Eomorphippus , as Simpson suspected. As AMNH FM 29405 and AMNH FM 29474 have not been described in detail previously, we incorporate observations from these specimens below. R. pascuali is intermediate between E. obscurus and E. neilopdykei in most dental dimensions (table 1), and is decidedly less hypsodont than both of those species.
LOWER DENTITION: The most complete lower dentition of R. pascuali known is the heavily worn AMNH FM 29474 (fig. 3E, F). Its sole preserved incisor, i3, is chisel shaped and fairly procumbent. The canine, sandwiched tightly between i3 and p1 (or dp1), is incisiform and about twice the mesiodistal breadth of i3. Neither the canine nor i3 show any indication of cingula or ridges on their lingual faces; enamel is restricted to above the alveolar border. The first premolar is remarkably little worn given the heavy abrasion of all succeeding cheekteeth except m3. Since this tooth is not usually replaced in notoungulates, it is typically heavily worn, if preserved at all. The very slight wear on the crests of the p1 (?dp1) of AMNH FM 29474 suggests either that this tooth was replaced late in ontogeny—after m3 had come well into wear—or that dp1 erupted unusually late in this taxon, either of which is an unusual and potentially taxon-diagnostic condition within the Notoungulata . A strong protoconid ridge dominates the crown of this tooth labially; a sinuous crest winds along the length of the tooth apically. The anterior end of this crest abuts the shallowly notched distal face of the canine. Posteriorly, this crest defines the top of a triangular labial hollow behind the anteriorly canted protoconid ridge. A very short cingulum occurs near the center of the base of the lingual face of the crown.
The p2 is slightly shorter than p1 anteroposteriorly (the remaining cheekteeth gradually increase in length posteriorly) but is of similar overall form. The lingual cingulum is better developed in p2 than p1, extending most of the length of the tooth. The third and fourth premolars are heavily worn in AMNH FM 29474, but it is clear that the greater labiolingual expansion of their trigonids and talonids (compared to p1–2) is not entirely attributable to wear. This is confirmed on the little-worn p3–4 of SGOPV 3051 (fig. 3G–I), which are also relatively broad. (The identities of some of the teeth preserved in SGOPV 3051 are open to question. The third tooth in the series is certainly m1 based on the shallow labial reentrant between the trigonid and talonid compared to the preceding teeth. Thus, the distalmost tooth, which is only partially erupted, is m2. The first molar shows very light wear, and the tooth preceding it is worn to only a slightly greater degree, arguing that it more likely represents p4 than dp4. Thus, we interpret the teeth of SGOPV 3051 as p3–m2.)
Although the trigonid of p3 of AMNH FM 29474 is damaged, there is clear evidence of a transverse metalophid; the hypolophid hooks lingually posteriorly, enclosing a small basin with an isolated entoconid within. A similar condition is present in p2 and p4 of AMNH FM 29474. In SGOPV 3051, a narrow but distinctly papillate basal cingulum rims the crown of p3 lingually, extending posteriorly from the terminus of the hypolophid apparently well into the trigonid (where breakage obscures its anterior end). If lingual cingula were ever present on the lower premolars of AMNH FM 29474, they have been obliterated by wear. The p3 cingulum in SGOPV 3051 compares closely to those seen in Pampahippus arenalesi and P. secundus from the Casamayoran of northern Argentina (Bond and López, 1993; Deraco and García-López, 2016). The labial face of p 3 in SGOPV 3051 is extremely similar to its counterparts in Eomorphippus obscurus , E. bondi , and AMNH FM 29474 in that the protoconid ridge is angular, projects quite far labially, and is canted strongly anteriorly. This creates a cleft between the trigonid and talonid that is much deeper and less vertical than the division between these structures on the molars.
The p4 of SGOPV 3051 resembles p3 overall. The p4 trigonid consists of the usual three lophids (meta-, para-, and protolophid), the first of which appears to have been the most elevated. Only the base of the paralophid is preserved, but it projects slightly posteriorly. A fairly wide, deep sulcus divides the paralophid and metalophid lingually; considerable wear would have been required to enclose a trigonid basin. The metalophid, the longest of three trigonid crests, roughly parallels the metalophid and runs anterolabially posterolingually. Its medial extremity thus projects into the sulcus between the trigonid and entolophid. Labially the p4 protoconid column is sharply angular and deep. The labial cleft between the trigonid and talonid on p4 is nearly vertical rather than canted anteriorly as on p3. The p4 cristid obliqua joins the metalophid centrally rather than at the metaconid as on p3. The talonid of p4 is less elongate (relative to tooth length) than on m1. Wear has reduced the entolophid into an anteroposteriorly broad platform that nearly meets a posterolingual projection of the metalophid anteriorly. With little additional wear these structures would have joined to enclose a small trigonid/talonid fossettid. A small notch at the posterolingual margin of the tooth separating the entolophid and the hypoconulid would have disappeared with little additional wear. A short, narrow, papillate cingulum encircles the base of the hypoconulid and the entolophid but fades away below the cleft between the entolophid and the medial spur of the metaconid. The basal portion of the central third of the tooth’s lingual face (below the metalophid) is smooth. A short cingulum may have occurred below the trigonid, but (as on p3) this point is obscured by breakage.
The occlusal surfaces of the first two molars of AMNH FM 29474 are essentially featureless due to wear. They preserve only slight lingual and labial constrictions of the enamel rim marking the trigonid/talonid connection. Fortunately, these teeth are reasonably well preserved on SGOPV 3051.
The m1 of SGOPV 3051 differs from the premolars primarily in the features noted above (rounded rather than angular posterolabial face of the trigonid, shallower labial cleft between the trigonid and talonid, elongate talonid), and in its lack of a lingual cingulum. Even though this tooth is otherwise little worn, the entolophid is already quite broad anteroposteriorly. An irregularly shaped basin is present between the entolophid and the posterolingually projecting spur of the metalophid. A minute cuspule fills the gap between the posterolingual extremity of the metalophid and the anterolingual corner of the entolophid, closing the basin lingually. Collectively these structures apparently would have worn into a short-lived fossettid, as no such fossette appears on the heavily abraded m1 of AMNH FM 29474. The groove between the entolophid and hypoconulid remains quite deep (3.0 mm) and anteroposteriorly broad (2.3 mm).
The second molar is just erupting through the gumline in SGOPV 3051, and none of its crests have yet come into wear. Other than wear-related distinctions, m2 differs from m1 mainly in its longer and straighter hypolophid. This results in a broad (4.8 mm) gap between the posterolingual terminus of the metalophid and the anterior face of the entolophid.
An isolated m3 from the Tinguiririca Fauna (SGOPV 3096) is only slightly more worn than the m3 of AMNH FM 29474, providing a superb point of comparison. The resemblance of the two teeth is striking. The specimen from Chile, SGOPV 3096 (AP = 21.8 mm, W= 9.0 mm), closely matches AMHH 29474 (AP = 23.0 mm, W = 9.4 mm) in size, degree of hypsodonty, and virtually every other morphological detail (fig. 3). The talonid of m 3 in AMNH FM 29474 is proportionally longer than on m2. The same is true when comparing talonid lengths (measured on the labial side of the teeth, from the trigonid/talonid sulcus to the posterior tooth margin at midcrown height) and total AP tooth length of SGOPV 3096 (16.6 mm / 21.8 mm) to this ratio in m2 of SGOPV 3051 (12.7 mm / 18.1 mm). The m3 hypolophid curves more strongly lingually at its posterior end than on m1–2 (where this structure is straighter). As on m1–2, the m3 trigonid is gently rounded buccally and thus lacks the distinct protoconid column present on the premolars. A triangular remnant of the sulcus posterolingual to the metalophid maintains a narrow connection to the lingual margin of m 3 in AMNH FM 29474; in SGOPV 3096 this connection has been severed by wear, resulting in an identically shaped but fully isolated fossettid. A similar comma-shaped cleft marks the posterior separation between the entolophid and the hypolophid. No cingula occur on either tooth. Enamel measures 9.8 mm in vertical height along the talonid-trigonid sulcus buccally in SGOPV 3096, and 6.9 mm at the level of the entolophid lingually. Overall the m3 of AMNH FM 29474 and SGOPV 3096 are so similar that the latter would look entirely in place in AMNH FM 29474 (if mirrored to the same side of the ramus).
UPPER DENTITION: The upper dentition of R. pascuali is best represented by AMNH FM 29405 , the holotype. Simpson (1967) provided a superb photograph of the specimen but only a limited description. Our description below draws mainly upon AMNH FM 29405 , but we also highlight its similarities to the referred material from Chile (i.e., SGOPV 2991 ). Although SGOPV 2991 is much more fragmentary, holding the two specimens side by side reveals their essential identity in size and all important occlusal details .
The second premolar is essentially quadrate. The ectoloph is mildly sinuous, bearing a marked paracone and parastylar nubbin. A saddle-shaped convexity separates the paracone column from a subdued posterior column on the labial face of the tooth. The P2 crown measures 6.8 mm in height along this saddle, and 4.2 mm in height across the protocone in SGOPV 2991. Therefore, this and all succeeding cheekteeth are unilaterally mesodont, being higher crowned labially than lingually. Cingula crossed the anterior and posterior margins of the tooth, but through wear these have joined with the occlusal surface except in the regions immediately anterior to and posterior of the elevated protocone. The medial portion of the anterior cingulum forms the deepest feature of the P2 crown. It is continuous posterolabially with the central fossa. The protocone slopes posteriorly and joins the ectoloph via a transverse crest (in the position of a molar metaloph). The protocone is isolated from the ectoloph anteriorly.
The third and fourth premolars strongly resemble the second except that they are progressively larger and bear stronger paracones. Since these teeth also are less worn, their anterior and posterior cingula are better preserved; neither loops across the lingual base of the protocone. The central fossa has become isolated as an obliquely oriented median valley on both teeth. The parastyles of P4–M2 are strong enough to imbricate over the posterolabial corner of the teeth preceding them.
The first and second molars are trapezoidal in outline, with the ectolophs and lingual margins approximately parallel to one another, the posterior margin perpendicular to both, and the anterior margin oblique anterolabially. They are much wider labiolingually relative to length than in either E. obscurus or E. bondi (in which the molars are much more longitudinal). The M1–2 ectolophs are subdued in their labial ribbing compared to the premolars. The paracone produces a mild swelling, but the metacone has essentially no column. The protolophs are well developed and angle well beyond the transverse midline of the teeth posteriorly. A small anterior bulge extends from the lingual end of the protoloph on M1. A strong cingulum occurs deep to the lingual half of the protoloph, its labial portion having coalesced with the occlusal surface. The lingual cingulum is much more feebly developed on M1 than on M2 and consists mainly of a small triangular shelf at the base of the nearly closed cleft between the protoloph and metaloph. The posterior cingulum was positioned much higher on the crown but through wear has already merged with the metaloph. The M2 is distinguished from M1 chiefly in its much stronger cingula, which encircle the tooth continuously anteriorly and lingually. The lingual cingulum is particularly broad, creating an internal “floor” to the crown that makes up approximately 20% of the transverse width of the tooth. The M2 also preserves two fossettes, a small posterolabial one in the vicinity of the metacone, and another (~ 1.5 mm in diameter) near the center of the former posterior cingulum now subsumed within the metaloph after wear. A small crest extends anteromedially from the lingual end of the metaloph, projecting into the broad trough between the protoloph and metaloph; the trough itself is continuous labially with the central fossa.
DISCuSSION: Simpson (1967) was reluctant to recognize “? Eomorphippus pascuali ” as distinct from Eomorphippus partly because of the uncertain association of the holotype (AMNH FM 29405), a partial maxillary dentition, and AMNH FM 29474, a mandible. Simpson collected AMNH FM 29474 at the same locality as the holotype, less than one meter higher than (and from the same faunal interval as) the holotype. The recovery of partial upper and lower dentitions remarkably similar to AMNH FM 29405 and AMNH FM 29474 from a second, geographically distant locale within a single narrow stratigraphic interval of the Abanico Formation of Chile, increases the likelihood that the two dentitions collected by Simpson at the Gran Barranca do in fact pertain to the same taxon (what he termed “? E. pascuali ”). A second reason Simpson hesitated removing “? E. pascuali ” from Eomorphippus was doubt about the significance of the slightly shorter lengths of p3–m 2 in AMNH FM 29474 relative to E. obscurus . Nevertheless, the new lower dentition from Chile (SGOPV 3051) confirms that the p3–m2 are consistently shorter (mesiodistally) in R. pascuali than in E. obscurus (table 1), answering the second of Simpson’s qualms about recognizing “? E. pascuali ” as distinct from Eomorphippus . Simpson (1967: 188) highlighted the lower crowns of “? E. pascuali ” in his diagnosis of the species, noting that such a marked difference in hypsodonty “would be almost incredible within one species.” Indeed, the greater hypsodonty of E. obscurus relative to “? E. pascuali ” seems to have been central to Simpson’s decision to recognize these taxa as distinct, possibly even above the species level. Building on Simpson’s leanings and with the reinforcing data provided by the new Chilean specimens, therefore, it is desirable to formally recognize the lack of an especially close relationship between Eomorphippus ( E. obscurus , E. bondi , E. neilopdykei ), and the former “? E. pascuali ” with a new binomial for the latter.
Although material of this small-bodied, low-crowned notohippid from the Tinguiririca Fauna at Termas del Flaco just described is quite distinctive, clearly closely resembles specimens from the Gran Barranca, and thus should be conspecific, determining which binomial should be applied to it is less straightforward. Mariano Bond (personal commun.) has pointed out similarities between material referred to “? E. pascuali ” by Simpson (1967) and the holotype of Pseudostylops subquadratus (Ameghino, 1901: 395) . Simpson (1936) had referred a partial palate (Feruglio field no. 31 = AMNH FM 27885 [cast]) to P. subquadratus but later (1967) placed this name in synonymy with Eomorphippus obscurus . The paltry holotype of P. subquadratus (MACN 10904), an upper premolar (probably P3), is a closer match to the corresponding tooth of the holotype of Simpson’s (1967) “? Eomorphippus pascuali ” than to the Feruglio specimen currently referred to E. obscurus . Nevertheless, we resist referring the new, readily identifiable specimens from Chile and Simpson’s excellent material from the Gran Barranca to Pseudostylops subquadratus given the scant material on which that name is based and the uncertain provenance of its holotype. We consider it preferable to apply a new name ( R. pascuali ) to this morphologically rich and biochronologically useful sample of fossils than to resurrect a name of such dubious utility and poor holotype material.
Notohippidae Ameghino, 1894 , incertae sedis
Unnamed large-bodied sp.
Figure 4
AGE: As for Eomorphippus bondi .
LOCALITY: As for Eomorphippus bondi .
REFERRED SPECIMENS: SGOPV 3004, partial incisor battery (probably upper) consisting of right I1-C and left I1; SGOPV 3062, isolated incisor (probably right I1). This taxon was previously referred to as “Notohippid new taxon A” ( Wyss et al., 1994) and as “undescribed taxon A” (Flynn et al., 2003).
DISCuSSION: A distinctive element from the Tinguiririca Fauna is an isolated partial anterior dental arcade (SGOPV 3004) bearing the complete incisor series and canine of one side, and the first incisor of the opposing side. Although we cannot entirely rule out the possibility that this battery represents lower teeth, factors detailed below lead us to regard them as uppers. (This specimen also conceivably represents R1-3 and L1-2, if one accepts a beguiling case of deformation.) In any case, the closed arcade formed by these teeth, as well as their subequal size, argues for assignment of this specimen to what has traditionally been conceived of as the Notohippidae rather than the Leontiniidae . The first two teeth are not enlarged (no matter which interpretation of tooth position is preferred), which rules out referral to the Leontiniidae assuming SGOPV 3004 belongs to an upper dentition; although the third tooth is slightly enlarged relative to the first two, it is not caniniform nor tusklike, as is characteristic of leontiniid lower incisors. This specimen also clearly does not pertain to Eomorphippus , whether it represents upper or lower teeth, thus indicating the presence of a second (in addition to E. bondi ) large-bodied notohippid in the Tinguiririca Fauna. SGOPV 3004 very likely represents a new taxon, and thus an additional notohippid within the Tinguiririca Fauna. Nevertheless, the two referred specimens consist solely of an uncommonly preserved portion of the dentition, thereby precluding comparisons to many previously named species. Such limited material also might hamper the future referral of specimens to the new taxon it represents, given that cheekteeth are more typically preserved than incisor arcades. Accordingly, we elect not to formally name this taxon at the present time.
Representatives of all elements of the anterior dentition are preserved in SGOPV 3004. Although these five teeth maintain their original positions relative to one another, only traces of bone adhere to the cluster, making it uncertain whether they pertain to the upper or lower dentition. The labiolingual robustness of these teeth (7–8 mm across the occlusal surface) relative to their breadth (8.5–11 mm), and the strong horizontal curvature of their converging roots suggest that they are uppers. The sizes of these teeth also suggest that they are uppers: the second incisor of SGOPV 3004 measures 8.6 mm mesiodistally, some 25% larger than i2 of Eomorphippus bondi . If SGOPV 3004 in fact represents part of a lower dentition, it would belong to an unusually large-bodied notohippid for Deseadan or earlier time.
The teeth of SGOPV 3004, all moderately worn,
form a smoothly rounded and fairly narrow arcade. In this regard, SGOPV 3004 more resembles Eurygenium pacegnum from the Deseadan of Bolivia ( Shockey, 1997)
than Eomorphippus . The occlusal surfaces of the incisors and canine are roughly equal in size and approximate rounded triangles in outline (curved side labial). These surfaces appear to be roughly parallel to a horizontal plane rather than steeply sloping lingually as in E. bondi .
The first two incisors and the canine are nearly equally broad mesiodistally. The third incisor exceeds I1 and I2
in breadth (by ~25%), crown height, and the girth of its root. All five teeth are exposed labially along their complete lengths, providing a clear view of their tapering,
closed, and strongly converging roots, as well as of the labial crown height. The incisors show no evidence of lingual or labial cingula. The canine, however, bears a pronounced, U-shaped (in labial view) cingulum at the base of its labial face. The upper incisors and canine are low crowned, which contrasts with the condition seen in species of Eomorphippus ; enamel is restricted to the FIGURE 4. Cast of SGOPV 3004, partial tooth tips (and presumably above the gumline), with the notohippid (unnamed large-bodied sp.) crowns measuring ~ 11 mm in height labially on I1 and incisor battery (probably upper) preserving right I1-C and left I1, in A, anterior I2 and ~ 13 mm on I3. This low level of incisor hypso- and B, occlusal views. donty in SGOPV 3004 (and 3062) is consistent with the modest level of unilateral (labial) hypsodonty exhibited by the cheekteeth of the leontiniid,
Termastherium , described below. These teeth also match well in size the cheekteeth referred to Termastherium . As mentioned, however, the pattern of tooth enlargement in SGOPV 3004
rules out leontiniid affinities regardless of whether the specimen represents an upper or a lower dentition (Bond and López, 1995; Shockey, 2005; Deraco et al., 2008).
REVISED DIAGNOSIS: Brachydont to mesodont toxodontians with upper cheekteeth generally higher crowned labially than lingually. Upper incisors caniniform. One upper incisor and third lower incisor enlarged to caniniform or tusklike form. Molar protolophs much longer than metalophs. “Leontiniid depression” on upper premolars of some taxa. Broad, robust entolophid of molars forms fossettid without involvement of posterior spur of metalophid or hypolophid, the latter of which is generally short (diagnosis modified as relevant to material in this study from Shockey, 2005, which in turn was modified from Chaffee, 1952, and Bond and López, 1995).
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