Neosclerocalyptus castellanosi, Zurita & Taglioretti & Zamorano & Scillato-Yané & Luna & Boh & Saffer, 2013

Zurita, Alfredo E., Taglioretti, Matias, Zamorano, Martin, Scillato-Yané, Gustavo J., Luna, Carlos, Boh, Daniel & Saffer, Mariano Magnussen, 2013, A new species of Neosclerocalyptus Paula Couto (Mammalia: Xenarthra: Cingulata): the oldest record of the genus and morphological and phylogenetic aspects, Zootaxa 3721 (4), pp. 387-398 : 390-393

Neosclerocalyptus castellanosi nov. sp.

Fig 1 A–E

Holotype. MPH 0114, partial skull and fragment of the dorsal carapace corresponding to the most antero-lateral region.

Etymology. Named in honor of Alfredo Castellanos (1893–1975), doctor and self-taught paleontologist, for his extensive and laborious dedication to the scientific study of glyptodonts.

Type locality. “ Las Antenas Militares” (38°14'23.75" S, 57°45'42.40" W), South of Mar del Plata city, General Pueyrredón, Buenos Aires province, Argentina ( Fig 2 ) .

Stratigraphic origin. Vorohué Formation, Marplatan Age/Stage, Vorohuean Subage/Substage (late Pliocene). Ctenomys chapadmalalensis Biozone (Cione and Tonni 1995, 2005; Cione et al. 2007) ( Fig 3 ).

Stratigraphic comments. The material described here represents the first record of a Neosclerocalyptus species from the Vorohué Formation (Vorohuean Subage, late Pliocene). Remains of Auliscomys cf A. osvaldoreigi ( MMP 5356) were collected from the infilling of an ancient vertebrate burrow situated at the same stratigraphic level where N. castellanosi was recovered. A. osvaldoreigi is a species restricted to the Ctenomys chapadmalalensis Biozone ( Quintana 2002) . Thus N. castellanosi sp. nov. cannot be more modern than Sanandresian Subage, according to the time averaged character of this bioconstruction. In this context, Kraglievich (1952) provided a litostratigraphic chart identifying those levels as Vorohuesian subage.

Diagnosis. Species of the genus showing the lowest degree of development of the ossified nasal cartilages, which are restricted to the antero-dorsal area of the nasals ( Fig 1 C ). Unlike that observed in N. pseudornatus , N. ornatus , N. gouldi , and N. paskoensis , the left and right sides of the ossified cartilages do not contact in the midline of the skull, occupying less than 40% of the dorso-ventral diameter of the skull in frontal view ( Fig 1 B ). Between these structures there is a “V” depression. The narial aperture ( Fig 1 A–B ) has a larger dorso-ventral and transverse diameter, related to the lower degree of development of the ossified nasal cartilage, and is more similar to that in Glyptodon than to that observed in the remaining species of Neosclerocalyptus . The ventral margin of the orbital notch is at the same plane as the lower part of the ossified nasal cartilage ( Fig. 1 A ), whereas in the other species the orbital notch is always located in a higher plane. The lachrymal tubercle is similar to but more developed than that of N. pseudornatus , and much more developed than that of N. ornatus , N. gouldi and N. paskoensis .

Description. The material corresponds to an adult specimen, and the cranial sutures are no visible. The general morphology of the skull resembles that of N. pseudornatus , but shows an evident lower degree of development of the ossified nasal cartilages.

In lateral view ( Fig 1 A ), these structures have the same globular morphology as in N. pseudornatus , thus clearly differing from that seen in N. ornatus , N. gouldi and N. paskoensis , in which they are much larger, completely covering the distal part of the nasals. The orbital notch has the typical subelliptical contour, dorsoventrally extended, but unlike that observed in the remaining species, its ventral margin is located at the same plane of the lower margin of the ossified nasal cartilage. In N. pseudornatus , N. ornatus , N. goudi and N. paskoensis , the ventral margin of the orbital notch is always placed at an upper plane. In turn, the distance between the anterior margin of the orbital notch and the ossified nasal cartilages is similar to that in N. pseudornatus . In N. paskoensis and N. gouldi , as a consequence of the larger development of the ossified nasal cartilages, both structures are in contact. The lachrymal tubercle is morphologically similar to that observed in N. pseudornatus , but more developed and thus, much more evident in this new species than in the other species. The zygomatic arch is more developed than in N. ornatus , N. gouldi and N. paskoensis , and is morphologically similar to that of N. pseudornatus (i.e, a quadrangular outline). As observed in all species of the genus, the postero-ventral margin of the zygomatic arch has a tubercle morphologically very similar to that of N. paskoensis . The descending process of the zygoma shows a strong dorso-ventrally extended crest.

In frontal view ( Fig 1 B ), the ossified nasal cartilage is quite similar to that of N. pseudornatus , but with some evident differences. The left and right sides do not contact in its midline, as in the other species of the genus. In N. paskoensis , N. gouldi , and N. ornatus , both ossified cartilages are separated by the sulcus supraseptalis and the septum nasi (Fernicola et al. 2012); in contrast, in this new species, both ossified nasal cartilages are limited to the latero-dorsal region of the nasals. In the midline of the nasals, there is a depressed area, suggesting that another structure could have been present. Compared with N. ornatus , N. gouldi and N. paskoensis , the differences are even more marked, because in these species the more evident development of the ossified nasal cartilage completely covers the distal area of the skull and, according to Fernicola et al. (2012), the narial aperture is in fact constituted by the apertura piriformis. Conversely, both in this new species and in N. pseudornatus , the lateral and ventral edges of the narial aperture are formed by the nasal, maxillaries and pre-maxillaries, being the ossified nasal cartilage limited to the latero-dorsal part of the narial aperture. Whereas in N. pseudornatus this cartilage occupies more than 50% of the total dorso-ventral diameter of the narial aperture in frontal view, in this new species, it represents less than 40%. As a consequence, the narial aperture is completely different, more similar to that of Glyptodon than to that of the other species of Neosclerocalyptus . In N. gouldi and N. paskoensis , the internal cavity is filled with a spongy tissue (maxilla-atrio turbinate), not observed in this new species.

In dorsal view ( Fig. 1 C ), the most differentiated area is that corresponding to the nasals, being the region constituted by the frontals, parietals and occipital similar to that of the other species of Neosclerocalyptus . Distally to the nasals, the ossified cartilages show a condition comparable to that observed in Neosclerocalyptus pseudornatus , but with some remarkable differences, especially with respect to a lower degree of development. As mentioned, the sides do not contact, but instead they are separated in the midline and restricted to a latero-dorsal location. In N. pseudornatus , both cartilages are in contact, whereas in N. ornatus , N. gouldi and N. paskoensis the left and right ossified nasal cartilages project distally and ventrally, related to the fact that the development is clearly more evident. Proximally, these structures are separated from the nasals by a marked groove, as in N. pseudornatus and N. ornatus , being in N. gouldi and N. paskoensis much less visible. One remarkable difference is that concerning the distal outline of the skull in dorsal view, which is sub-circular in all species except in this new species, in which it acquires a more quadrangular morphology, similar to that in Glyptodon or Plohophorus Ameghino. The parietal and occipital areas of the skull do not show significant differences from those of N. ornatus and N. pseudornatus .

In occlusal view ( Fig 1 D ), the most noticeable difference is that the ossified nasal cartilages are not visible; in contrast, this structure is clearly observable in all the other species, being more evident in N. ornatus , N. gouldi and N. paskoensis . Only the distal half of the palate is preserved, except for the pre-maxillae. This preserved part does not show significant differences with the other species. Although only the M5 is preserved, it is possible to infer the morphology of the M1–M4, which are very similar to those of the other species of the genus.

The dorsal carapace preserved corresponds to the most antero-lateral area and is constituted by 76 associated osteoderms ( Fig 1 E ). The general morphology of the osteoderms is similar to that known for the other species ( Zurita 2007). The exposed surface of the osteoderms is highly eroded, thus precluding the observation of the real pattern of ornamentation.

Phylogenetic analysis. The cladistic analysis resulted in one most parsimonious trees (TL: 30; CI: 0.967; RI: 0.978). The topology of the tree obtained is similar to that previously obtained ( Zurita et al. 2013) ( Fig 4 ). It is possible to recognize two large basal natural groups: one constituted by the subfamily Glyptodontinae ( Glyptodon + Glyptotherium ) (12:1; 14:1; 21:1) and another one supported by a single synapomorphy (18:1). In this latter clade (19:1; 22:1) a basal polytomy is observed among the taxa D. clavicaudatus , P. figuratus and the clade constituted by Panochthus + Hoplophorus , and Neosclerocalyptus spp , which is supported by one synapomorphy (17:0). In turn, the clade constituted by P. intermedius + H. euphractus (10:1; 11:1; 19:2; 20:1) appear as sister taxa of Neosclerocalyptus spp. This phylogenetic hypothesis is in agreement with that proposed by Fernicola (2008), Porpino et al. (2009, 2010), Zamorano (2012a,b), Zamorano & Brandoni (2013), and Zurita et al. (2013). In turn, the genus Neosclerocalyptus appears as an evident natural group, a condition supported by four synapomorphies: distal area of the skull with ossified nasal cartilages (0:1); morphology of the distal area of the nasals modified into a single globular structure (1:1); cephalic armor presenting an evident rectangular contour (13:1); and dorsal carapace low and elongated, sub-cylindrical, and with dorsal outline almost straight (15:1). Within Neosclerocalyptus , two main clades can be recognized. One of them is composed of the Bonaerian and Lujanian species ( N. gouldi + N. paskoensis ). The synapomorphies supporting this condition are: distal margin of the rostrum constituted by the ossified nasal cartilages, which are straight (3:2); the presence of an evident septum nasi separating both ossified nasal cartilages (6:1); the presence of a spongy tissue in the distal area of the nasals (7:1). The other clade is formed by the Ensenadan and Vorohuean species ( N. ornatus + N. pseudornatus + N. castellanosi sp. nov. (5:1; presence of a “V” groove separating the modified nasal area from the rest of the skull). There, N. ornatus is positioned as the sister taxon of N. pseudornatus + N. castellanosi sp. nov; both species are characterized by the following synapomorphies: morphology of the distal area of the nasals modified into a globular structure with two protuberances (1:2); antero-posterior development of the ossified nasal cartilages representing less than the 10% of the total length of the skull (2:0); ventral edge of the orbital notch coinciding with the lower half of the ossified nasal cartilages (4:0); distance between the anterior edge of the orbital notch and the posterior border of the ossified nasal cartilages larger than the antero-posterior diameter of the orbital notch (8:0).

Figures

FIGURE 1. Neosclerocalyptus castellanosi sp. nov. (MPH 0114). Skull in A, lateral, B, frontal, C, dorsal and D, ventral views. E, associated osteoderms belonging to the most antero-lateral region of the dorsal carapace. F (a–d) Neosclerocalyptus pseudornatus (MACN-Pv 8579); (e–h) Neosclerocalyptus ornatus (MLP 16–28); (i–l) Neosclerocalyptus gouldi (MCA 2010); (m–p) Neosclerocalyptus paskoensis (MACN-Pv 18107). Scale bar: 100 mm.

FIGURE 2. Map showing the locality where the type specimen (MPH 0114) of Neosclerocalyptus castellanosi sp. nov. was recovered.

FIGURE 3. Lithostratigraphic profile showing the fossiliferous level.

FIGURE 4. Phylogeny of Glyptodontidae based on TNT analysis of 22 osteological characters in 13 taxa (TL: 30; CI: 0.967; RI: 0.978). The numbers above each node represent bootstrap values; numbers in bold show Relative Bremer support.