Orocavia andina ( Rovereto, 1914 ) Jaén & Pérez, 2024

Jaén, María Carolina Madozzo & Pérez, María Encarnación, 2024, Redescription of a small Caviidae (Rodentia: Hystricognathi) from the Neogene of northwestern Argentina and its systematic implications, Comptes Rendus Palevol 23 (20), pp. 269-292 : 275-282

Orocavia andina ( Rovereto, 1914) n. comb.

( Figs 3-7; Tables 1-3 )

Dolichotis andina Rovereto, 1914: 58 , fig. 25.

Orthomyctera (Orocavia) andina Kraglievich, 1932: 163 .

TYPE MATERIAL. — Holotype. Argentina. MACN-Pv 8350, skull with articulated atlas, complete upper dental series, and left mandibular fragment with i, p4-m3.

REFERRED MATERIAL. — MACN-Pv 8300, right mandible fragment with p4-m3; MACN-Pv 8347, palatal fragment with right P4-M2 and fragment of M3 and left P4-M1; MACN-Pv 8349, left mandible fragment with p4-m2; MACN-Pv 8351, fragment of skull with complete dental series; MACN-Pv 8399, fragment of skull with complete dental series; MACN-Pv 8401, fragment of skull with complete dental series; MACN-Pv 8402, palatal fragment with complete dental series; MACN-Pv 8403, palatal fragment with left P4-M3 and right P4-M2; MACN-Pv 8404, palatal fragment with left M1-M3 and right P4-M1; MACNPv 8409, palatal fragment with left M1-M3; MACN-Pv 8411, right mandible fragment with m1-m3; MACN-Pv 8412, right mandible fragment with p4-m3; MACN-Pv 8414, left mandible fragment with p4-m3; PVL 3293, left mandible fragment with p4-m3; FMNH P 14464, fragment of skull with complete dental series; FMNH PM 1094, fragment right mandible p4-m2; FMNH P 14370, fragment of skull with complete dental series and atlas; PVL 4892, fragment of skull with complete dental series; MCH-P 90, fragment of skull with right complete dental series and left P4-M2 and anterior lobe of M3; MCH-P 91, fragment of skull with left M1 and right M1-M2; MCH-P 94, left mandible fragment with p4-m2; MCH-P 345 right mandible fragment with p4-m2; MCH-P 346 left mandible fragment with m1-m2; MCH-P 360 left mandible fragment with m1-m2; MCH-P 361 left mandible fragment with m1-m2; MCH-P 366 maxilla fragment with right P4-M2 and fragment of M3 and left P4-M1 and left mandible fragment with m1; MCH-P 367 left mandible fragment with p4. The provenance of each referred material is detailed in Appendix 9.

MODIFIED DIAGNOSIS. — Caviinae diagnosed by the following unique combination of characters (apomorphies marked with an asterisk): cheek teeth euhypsodont, bilobed, and each heart-shaped; constriction in the apex of each lobe present; hypoflexus/ id funnel-shaped; dentine crest in the middle of occlusal surface in each lobe; cement in the hypoflexus/id present; *furrow opposite to hypoflexus/ids present as in Dolichotinae , differing from the other Caviinae ( Galea , Cavia , Microcavia , Palaeocavia , Neocavia , Dolicavia , and Orthomyctera ); enamel interrupted on the labial side in upper cheek teeth, and on the medial side in lower ones, except on the furrow opposite to hypoflexus/id; M1 shorter and M3 longer than the other cheek teeth as in O. rigens ; posterior projection of M3 anteroposteriorly long, shorter than in Dolicavia ; anterior projection of p4 anteriorly well-developed differing from Palaeocavia and Cavia . Lateral ridge of the infraorbital groove absent; posterior portion of diastema oblique and shorter than in Cavia aperea Erxleben, 1777 and Galea leucoblephara , differing from O. rigens , Microcavia and Dolicavia . Terraced palate shallower than in Neocavia , O. rigens , Dolicavia , and M. australis . Tympanic bullae with respect to skull length are large as Dolicavia , M. australis , and Neocavia , but smaller than in N. lozanoi . External auditory meatus more ventral respect to the occlusal dental series, as in Dolicavia , M. australis , and N. lozanoi . Notch for insertion of the tendon of the masseter medialis pars infraorbitalis muscle is deeper depth than dorsal fossa of horizontal crest.

TYPE LOCALITY. — Argentina, Andalhuala locality, Catamarca Province, Santa María Valley. Late Miocene-early Pliocene (“Araucanian”).

GEOGRAPHIC AND STRATIGRAPHIC PROVENANCE. — Santa María Valley , Catamarca Province: in Andalhuala and “Al sureste de ex Chiquimil”, [Southeast from ex Chiquimil] Entre Ríos localities, without precise stratigraphic data (Late Miocene-Early Pliocene, and “Araucanense”; Marshall & Patterson 1981); Entre Ríos (ex Chiquimil) locality, Andalhuala Formation, in levels XVIIIa and XVIIIb; Loma Rica locality in level XVII (Late Miocene, Marshall & Patterson 1981). Villavil-Quillay basin, Catamarca Province in Villavil locality, Chiquimil Formation, El Jarillal Member, (Late Miocene, Powell et al. 1998; Esteban et al. 2014); Western Slope of Cerro Pampa (San Fernando Sur locality), Andalhuala Formation (Late Miocene-Early Pliocene; Bonini et al. 2021).

DESCRIPTION AND COMPARISON

Cranium

The anteroposterior length of Orocavia andina n. comb. is approximately similar to that of Orthomyctera rigens ( Fig. 2), larger than in M. australis and smaller than Dolicavia (Appendices 4; 5). The APL of the rostrum in relation to APL of the skull is larger than in M. australis (approximatively 7.5% longer) and Dolicavia (approx. 4% longer). The width of the braincase is smaller than in Dolicavia (approximatively 20% less) and somewhat larger than in M. australis and Neocavia lozanoi (approximatively 10% longer) Table 1 ; Appendices 4; 5).

Nasal. The nasals are better preserved in the holotype, but the anterior portion is missing ( Fig. 4A). In dorsal view, this bone is relatively wider than in M. australis , and narrower than that of Dolicavia . The nasofrontal suture is anteriorly concave ( Fig. 4 A-C) as in Dolicavia or slightly concave ( Fig. 5A) as in M. australis . In lateral view, the nasal is dorsally convex in the medial portion ( Fig. 6A, B; Appendices 4; 5).

Premaxilla. In dorsal view ( Figs 4A; 5A), the dorsal process of the premaxilla is narrow along the contact with the nasal, widening posteriorly. In lateral view, the alveoli of the upper incisors are broken in all the specimens that preserve this portion ( Figs 4B, C; 6A). The premaxillary portion of the rostral masseteric fossa is shallow as in Dolicavia . The premaxillamaxilla suture in the lateral wall of the rostrum is unclear in the holotype because this region is deteriorated ( Fig. 4B, C).

In ventral view, the suture is located on the posterior half portion of the diastema, as in Dolicavia and M. australis . Approximately 75% of the margins of the incisive foramen are formed by the premaxilla. This foramen ( Figs 4D; 5D) is similar in size and shape to those of Dolicavia , Microcavia (Appendices 4; 5).

Maxilla. In lateral view, the maxillary portion of the rostral masseteric fossa is in the middle of the rostrum ( Figs 4B, C; 6A), this fossa is less developed than in M. australis . At the P4 level, a lateral vacuity of the nasolacrimal duct (nasolacrimal foramen sensu Ubilla et al. 1999; maxillary lacrimal canal sensu Cherem & Ferigolo 2012) is present ( Fig. 6C). This vacuity is present in Caviinae and Hydrochoerinae (e.g. Hydrochoerus ), but absent in Dolichotinae (e.g. Dolichotis ). In the posterior portion of the diastema, the maxilla is obliquely oriented respect to alveolar line ( Figs 4B, C; 6G), and this condition differs from M. australis , Dolicavia , and N. lozanoi (see above). The lateral ridge of the infraorbital groove is absent. It differs from O. rigens , N.lozanoi , Dolicavia , and M. australis , in which it is present. The sphenopalatine foramen is between groove infraorbital and alveolar protuberances of P4 and M1 ( Cherem & Ferigolo 2012; Fig. 6D, E). Dorsally to the alveolar protuberance of M2 ( Fig. 6 C-E), the lacrimomaxillary fissure (sensu Cherem & Ferigolo 2012) extends posteriorly. The maxillary process of the zygomatic arch originates at the level of P4, anteriorly is elongated and dorsoventrally low ( Fig. 6 A-F). In ventral view, the origin of the zygomatic arch presents a shallow notch of the tendon of the medial part of masseter muscle ( Fig. 5D). This notch is an elliptical concavity with well-defined edges in O. rigens ( Fig. 2D) and Dolicavia (Appendices 4; 5). The palate is triangular and terraced; the central portion is more dorsal than the alveolar border but this difference is less marked than Neocavia , O. rigens , Dolicavia , and M. australis ( Figs 2D; 4D; Appendices 4; 5).

Palatine. The notch for the minor palatine nerve and vessels (sensu Wible et al. 2005) is medial to the posterior projection of M3 ( Fig. 5C). Some specimens ( Fig. 5D, F) have preserved a palatine crest on the middle line that extends up to the M1-M2 level. The anterior apex of the mesopterygoid fossa is U-shaped and anteriorly extended up to the level of the anterior lobe of M3 ( Figs 4D; 5D), as in M. australis . The anterior margin of sphenopalatine vacuity (sensu Cherem & Ferigolo 2012); is limited by palatine and medially by the presphenoid; the posterior margin is not preserved ( Fig. 5C).

Frontal. In dorsal view, the nasal process of the frontal (sensu Cherem & Ferigolo 2012; i.e., the anterior projection of the frontal, between the nasal and the premaxilla) is triangular-shaped and conspicuously extended anteriorly in the holotype ( Fig. 4A); whereas in MACN-Pv 8351 ( Fig. 5A) is not anteriorly projected. The interorbital width is similar to that of M. australis and smaller than in Dolicavia (Appendices 4; 5). The contacts with parietals are straight as M. australis , D. minuscula .

Parietal. The parietal is dorsolaterally convex ( Fig. 4A), as in O. rigens Dolicavia , M. australis (Appendices 4; 5), and N. lozanoi , but differs from D. patagonum which have anterior portion slightly convex (see Rovereto 1914). The temporal fossae are shallow and do not developed a sagittal crest; there is a differentiated plane area named the “interposed flat zone” by Quintana (1998) Fig. 4A), as in Dolicavia and M. australis . The specimens of Or. andina n. comb. consists of adult individuals in which the interparietal is not recognized; this condition differs from Dolicavia in which the interparietal is not fused with the parietal in adult specimens. This region is deformed in other skulls of Or. andina (e.g. MACN-Pv 8351, MACN-Pv 8401; Figs 5A; 6E).

Lacrimal. In lateral view, the anterodorsal portion of the zygomatic arch of the holotype ( Fig. 4C) has a fragmentary bone interpreted here as a portion of the lacrimal with the moderately developed facial process. In other specimens, the lacrimal is very fragmentary ( Fig. 6E).

Jugal. In lateral view, in the holotype ( Fig. 4B) only preserved the jugal-squamosal suture, which is posterior to M3. The maxilla-jugal suture of FMNH-P 14370 ( Fig. 6A) is indistinct for bad preservation. In contrast, the contact with the squamosal is anteriorly convex and ventrally straight. The maximum height (2.5 mm) of jugal is at the level of the M3. The insertion of the deep part of the masseter muscle is ventral in the anterior portion and lateroventral in the posterior portion ( Fig. 5D), as in Dolicavia . This condition differs from that of M. australis in which in the anterior portion the insertion is lateral (Appendices 4; 5).

Squamosal. The exposed dorsal surface of the squamosal is larger than in Dolicavia and M. australis ( Figs 4A; 5A). In lateral view, the zygomatic process of the squamosal is narrow ( Figs 4B; 6A). The caudal process of the squamosal is anteroposteriorly straight, and the posterior portion is ventrally projected penetrating between the bulla and the occipital complex ( Figs 4B; 6D, E). It differs from Dolicavia and M. australis in that the posterior projection is less ventrally extended. We interpreted as postglenoid (or retroarticular) foramen, an oval-shaped fissure between the caudal process of the squamosal and epitympanic region of the tympanic bulla ( Fig. 4B, C). A posterior and smaller circular-shaped fissure could correspond to the foramen for ramus temporalis ( Wahlert 1974; Wible et al. 2005; Wible 2011).

Tympanic bulla. In lateral view, the tympanic bullae are prominent ( Figs 4B, C; 6A, D-G), proportionally smaller than in N. lozanoi but larger than in the other cavies ( Table 1 ; and see Madozzo Jaén et al. 2018; and reference there). Dorsal and posterior to the external auditory meatus, the epitympanic sinus (pet) is laterally inflated ( Fig. 4B, C), differing from Dolicavia and M. australis in which the pet is less bloated. The mastoid portion of the petrosal (pmp) is flat in the dorsal half and convex in the ventral half, whereas in Dolicavia and M. australis , the pmp is convex in all extensions. The external auditory meatus (mae) is broad and rounded, central in the tympanic bulla; it is located below the level of the dental series ( Figs 4B, C; 6A, D, E) as in Dolicavia , M. australis , and N. lozanoi . In some specimens, a rim surrounds the meatus, it is incomplete on the dorsal edge ( Figs 4B, C; 6 D-G). The circular infratympanic fenestra is small and ventral to mae, in MACN 8401 it is isolated to mae, the other specimens are connected, possibly due to poor preservation and the stylomastoid foramen is posterior to mae ( Fig. 6F, G). It is remarkable the marked skull flexion (the angle that the palate forms with the basicranium, and the foramen magnum opening posteroventrally), as in Microcavia , Dolicavia and Neocavia . In ventral view ( Figs 4D; 5 C-E), the major axis of the tympanic bulla is approximately 45% of the APL of the skull ( Madozzo Jaén et al. 2018: table 1). This proportion is smaller than in N. lozanoi (50%) and larger than in M. australis [40%] and C. aperea [28,5%] (see Madozzo Jaén et al. 2018). The posterior lacerate foramen (sensu Cherem & Ferigolo 2012) is a fissure between the tympanic bullae and the occipital condyle ( Fig. 5 C-F). Other structures, such as the apertures for the passage of vessels and nerves, are concealed by sediment.

Presphenoid and basisphenoid. In both bones, the anterior half is narrower than the posterior portion. The basisphenoid has a ridge in the midline at the anterior two-thirds of its length ( Fig. 5 C-E).

Alisphenoids. In ventral view, the alisphenoid ( Fig. 5C, F) is thicker than in M. australis and Dolicavia , in which it is a thin lamina (Appendices 4; 5; see Quintana 1997). The foramen ovale opens in the alisphenoid, the medial and ventral margins of this bone are concave and form the margin of the foramen, the medial margin of the foramen ovale is not preserved. The accessory ovale foramen is smaller and more lateral than the foramen ovale ( Fig. 5F; Wahlert 1974). Posteriorly, between the alisphenoid and tympanic bullae, a small foramen ( Fig. 5F) could correspond to the exit of the eustachian canal ( Wahlert 1974). Cherem & Ferigolo (2012) named, in Cavia , this foramen as carotid foramen, but this one should be located adjacent to the central stem, medial to the foramen ovale, and directly lateral to the position of the hypophysis ( De Beer 1937).

Occipital complex. In ventral view, the basioccipital is rectangular, widening posteriorly, following the medial outline of the tympanic bulla ( Figs 4D; 5C, D, F). The aperture for the inferior petrosal sinus ( Fig. 5C) is between basioccipital and the tympanic bulla, which does not present a marked notch for the foramen, as in Dolicavia (e.g. PVL 3745; PVL 3765, Appendices 4; 5). The paraoccipital apophysis is broken in all specimens, but in lateral view, it extends at least below the level of the external auditory meatus ( Figs 4B, C, E; 5E).

In posterior view, the holotype (other specimens are deformed; e.g. Fig. 5E) has a rounded outline dorsally and laterally with the foramen magnum opening posteroventrally somewhat smaller than in Dolicavia . The external occipital crest of the exoccipital is a low ridge ( Figs 4E; 5E); it is similar to M. australis but differs from Dolicavia , in which it has a well-defined ridge (Appendices 4; 5). The ventral nuchal crest is slightly developed ( Figs 4E; 5E). The occipital articulates with the atlas in the holotype and FMNH-P 14370 ( Figs 4E; 5D see below). In dorsal view, a small portion of the supraoccipital ( Figs 4A; 5A) is exposed as in the other cavies. The occipital condyles have a medial-ventral orientation-laterodorsal orientation, with a thickening in the central part.

Mandible

The dentary is more robust than in M. australis and N. lozanoi , and smaller than in Dolicavia ( Quintana 1996, 1997; Madozzo Jaén et al. 2018). In lateral view ( Figs 4F; 7B, C), the orientation of the anterior portion of the diastema is oblique with respect to the dental series. The mental foramen is anterior to p4, at the dorsoventral middle point of the mandible, more dorsal than in M. australis and Dolicavia . The mental process (chin) is moderately developed as in Microcavia . The lateral crest is almost straight, and the notch for the insertion of the tendon of the masseter medialis pars infraorbitalis muscle (nMpi) is located between m1-m2, similar to Dolicavia , M. australis , and N. lozanoi . The horizontal crest is well-developed, forming a laterally projected shelf that connects to the nMpi as in the other caviids ( Fig. 7B, C; see Rovereto 1914). The depth of the dorsal fossa for masseter medialis insertion is less than that of the nMpi. ( Fig. 7H). In the ventral margin, the alveolar protuberance of m1 is well-developed ( Figs 4F; 7C). In medial view, the incisor extends posteriorly to the level of the posterior lobe of m1, differing from Dolichotis in which the incisor is extended more posteriorly ( Kraglievich 1932). The mylohyoid crest is present as in Dolicavia and the pterigoid fossa is shallow, only preserved in MACN 8349 ( Fig. 7E, F). The mandibular foramen is at the level of m3. The coronoid and angular process and the condyle are not preserved in any specimens.

Cheek teeth

The cheek teeth are anteriorly convergent into the palate, these are euhypsodont and double heart-shaped, with a constriction in the apex of the lobes, and with a transverse dentine crest in the middle of the occlusal surface of each lobe, as in other Caviinae and Dolichotinae ( Figs 3B - F; 7H, I). The molariforms have a furrow opposite the hypoflexus/ id, as in Dolichotis and Prodolichotis ( Dolichotinae ). This condition differs from that of Cavia , Dolicavia , Neocavia , Microcavia , Palaeocavia , and O. rigens in which are external secondary flexus (HSE) and primary internal flexid (hpi), and from Galea that has HSE and primary external fissure (HPE) in and hpi. In Or. andina n. comb. the hypoflexus/ id (HFI/hse) are funnel-shaped with cement; the enamel is interrupted on the labial wall of the upper molariforms and on the lingual wall of the lower ones, except in the furrow opposite the hypoflexus/id, which resembles the condition of Caviinae and Dolichotinae .

The upper incisors have an orthodont position ( Figs 4B; 6A), differing from the condition of Dolicavia , in which the position of the upper incisors are proodont (Appendices 4; 5). The APL of P4 is subtly larger than M1; M2 is larger than M1, and M3 is larger than the other molariforms ( Table 2 ). The third molar has a well-developed projection in the posterior lobe, which is posteriorly oriented. The angle between the

posterior lobe and the posterior projection is slightly variable between specimens ( Figs 3 B-F; Table 2 ). The configuration of M3 of Or. andina n. comb. is similar to Dolicavia , differing from Dolichotis ( Rovereto 1914) and M. australis , in which the posterior projection is developed as an incipient third lobe with cement in the flexus formed with the posterior lobe (Appendices 4; 5). The APL of p4 is smaller than m1, m1 is smaller than m2, and m2 is smaller than m3 ( Table 3 ; Figs 4H; 6 F-H; 7H, I). The projection of the anterior lobe of p4 is somewhat variable in size; the m1 and m2 are similar, more similar to each other than to the other molars, and the posterior lobe of the m3 has the larger APL.

Atlas

The atlas is preserved articulated with the occipital in the holotype and FMNH-P 14370 ( Figs 4D, E; 5D). In caudal view, the anterior margin is roughly straight with the spinous process broken, and the posterior margin is posteriorly concave. In the holotype, the alar foramen is anterolateral, on the transverse process ( Figs 4D, E). In addition, the ventral tubercle, ventral arch, and caudal articular fovea are broken in ventral view.

REMARKS

In the original description of Dolichotis andina, Rovereto (1914) figured upper and lower right cheek teeth ( Rovereto 1914: fig. 25). About the mandible he clarified “La serie dentaria es derecha” (the dental series is right). Kraglievich (1932) assigned that species to Orthomyctera (Orocavia) and redescribed it based on a skull and mandible. He considered the skull MACN-Pv 8350 as the type. Posteriorly, Kraglievich (1934) briefly redescribed the type MACN-Pv 8350, including the skull and the mandible. In none of the publications Kraglievich (1932, 1934) clarified whether the jaw is right or left.

Currently, the collection number MACN-Pv 8530 includes a skull and a left mandible (not right as published Rovereto) and is considered as the type of Orthomyctera (Orocavia) andina (synonym of Dolichotis andina ). The left mandible was missing for a while but was recently relocated, and the size and morphological characters match with those of the skull. Here, it is considered that the holotype MACN-Pv 8350 is composed by the skull and the left mandible.

PHYLOGENETIC ANALYSIS

The combined cladistic analysis resulted in a total of 1774 most parsimonious trees (MPTs) of 3438 steps, a strict consensus of all trees was calculated (see Fig. 8A; Appendix 10). Orthomyctera rigens and Orocavia andina n. comb. are included within Caviinae ( Fig. 8). Orocavia andina n. comb. is placed as the sister taxon to the clade encompassing the species of Microcavia , Dolicavia , Neocavia , and Orthomyctera ( Fig. 8, node A). It is supported by six unambiguous synapomorphies: flat area between temporal fossae (character [c.] 45, state [s.] 0); external auditory meatus below the occlusal surface (c. 54, s. 1); anterior-posterior length of posterior border of the upper diastema up to 10% of maxilla (c. 56, s. 0); posterior margin of the incisive foramina wide (c. 58, s. 1); terraced palatal surface (c. 59, s. 3); length of p4-m1 shorter than the length of m2-m3 (c. 125, s. 0). Orocavia andina n. comb. has three unambiguous apomorphies: furrow opposite to hypoflexus/id in p4 [c. 86, s. 0]; m1-m2 [c. 117, s. 0] and M1- M2 [c. 142, s. 0]. The Microcavia , Dolicavia , Neocavia , and Orthomyctera rigens clade ( Fig. 8, node B) is supported by three synapomorphies: anteroposterior length of the upper diastema shorter than the molariform series (c. 47, s. 1); posterior border of superior diastema vertical (c. 55, s. 1) and labial projection on the anterior lobe is present in M1-M2 [c. 138, s. 1).

Dolicavia is the sister group of the clade formed by O. rigens and Neocavia lozanoi , N. pampeana and Neocavia sp. ( Fig. 8, node C). The clade that includes O. rigens and Neocavia ( Fig. 8A, node D) collapses in a polytomy generated by the instability of Orthomyctera (see the alternative resolutions in Fig. 8B). This node is supported by three unambiguous synapomorphies: the root of the lower incisors extended up to the level of the anterior lobe of m1 (c. 20, s. 4); developed lateral ridge of the infraorbital groove (c. 51, s. 1); anterior projection on the prI of p4 absent (c.82, s.0).