Macrochorobates scalabrinii

Macrochorobates scalabrinii (Moreno and Mercerat, 1891) (= Macrochorobates chapalmalensis Ameghino, 1908 new synonymy) (Figs 2–7; Supporting Information, S3) Type material:?MLP-PV articulated fragment of the pelvic shield (Lydekker 1895: pl. XXXIII, fig. 6). This material (Fig. 2A) was published without a collection number and, according to Scillato-Yané (1982) and Mones (1986), it is not housed in the Museo de La Plata. We were unable to locate the type material. Type locality and age: Valle de Santa María, Catamarca Province, Argentina. ‘Araucanian’, Late Miocene–Pliocene. Material referred Macrochorobates scalabrinii: CC529, almost complete articulated dorsal carapace; CRILAR-Pv-120, fixed and mobile osteoderms; CRILAR-Pv-420, fixed and mobile osteoderms; CRILAR-Pv-131, fixed and mobile osteoderms; FMNH-P14360, almost complete skull; FMNH-P14493, mandible; FMNH-P14510, cephalic shield fragment, nuchal osteoderms, almost complete articulated dorsal carapace including scapular shield, mobile bands, and pelvic shield, skull fragment including occipital area, cervical vertebrae, and distal left femur; FMNH-P14784, left hemi-mandible fragment; FMNH-P15435, skull fragment including parietal, posterior palatal, and basicranial area; FMNH-PM880, articulated dorsal carapace fragment including the last mobile band and pelvic shield; FMNH-PM1089, left hemi-mandible fragment, nuchal, mobile, and lateral osteoderms; IANIGLA-PV-120, articulated pelvic shield fragment; IBIGEO-P33, fixed osteoderm; IBIGEO-P37, fragmented mobile osteoderm; INGEO-PV-235, fixed osteoderm; JUY-P-0090, cephalic shield, fixed and mobile osteoderms; MACN PV 5345, fixed osteoderms; MACN PV 8134, left hemi-mandible fragment; MACN PV 8138, right hemi-mandible fragment; MACN PV 8144, right hemi-mandible fragment; MACN PV 8217, osteoderm fragments; MACN PV 8271, fragment of both hemi-mandibles; MACN PV 8283, left hemi-mandible fragment, mobile osteoderms; MMH-CH-84-04-56, mobile osteoderm; MMH-CH-84-04-66, mobile osteoderm; MMH-CH-85-04-113, fixed osteoderm; MMH-CH-87-7-6, mobile osteoderm; MMH-CH-87-7-69, mobile osteoderm; MMH-CH-88-6-6-6, fixed osteoderm; MMH-CH-88-6-13, fixed osteoderm; MMH-CH-88-6-15, fixed osteoderm; MMH-CH-10-4-66, mobile osteoderm; PULR-V-190, fragmented osteoderm; PULR-V-191, fragmented osteoderm; PULR-V-192, fixed osteoderm; PVSJ-652, mobile and fixed osteoderms, semi-mobile osteoderms of the scapular shield and semi-mobile osteoderms of the pelvic shield. Materials previously referred to Macrochorobates chapalmalensis: MACN PV 5825 (originally defined as the holotype of this species), mobile and fixed osteoderms; MACN PV 5908, mobile osteoderm; MACN PV 6482, mobile and fixed osteoderms, right femur and tibia-fibula fragment; MACN PV 7573, palate fragment; MACN PV 7889, articulated dorsal carapace fragment including nuchal osteoderms, scapular shield bands, and mobile bands; MACN PV 10267, left hemi-mandible fragment; MACN PV 10270, mobile osteoderms; MACN PV 16950, mobile osteoderms; GHUNLPam 5066/5, fixed osteoderm; GHUNLPam 5976/1, mobile osteoderm; GHUNLPam 2291/55, mobile osteoderm; GHUNLPam 8198/96, fixed osteoderm. Geographic and stratigraphic provenance and age: Buenos Aires Province: Cerro Azul (Late Miocene), Monte Hermoso (Early Pliocene), and Chapadmalal (Late Pliocene) formations (Scillato-Yané 1980, 1982, Barasoain et al. 2018); La Pampa Province: Cerro Azul Formation (Late Miocene–Early Pliocene) (Urrutia et al. 2008); Mendoza Province: Huayquerías (Late Miocene) and Tunuyán (Early Pliocene) formations (Romano and Esteban 2019, Romano et al. 2023); San Juan Province: Las Flores (Late Miocene) and Loma de Las Tapias (Late Miocene) formations (Contreras et al. 2013); La Rioja Province: Salicas (Late Miocene) and Toro Negro (Late Miocene) formations (Barasoain et al. 2022b, Brandoni et al. 2023, Ruiz-Ramoni et al. 2023); Catamarca Province: Chiquimil (El Jarillal Member, Late Miocene) and Andalhuala (Late Miocene–Early Pliocene) formations (Esteban et al. 2014); Tucumán Province: Tío Punco outcrops (Late Miocene–?Early Pliocene) (Scillato-Yané 1982); Salta Province: Palo Pintado Formation (Late Miocene) (Zimicz et al. 2018); Jujuy Province: Uquía (Late Pliocene), Maimará Formation (Late Miocene), and an unnominated formation (Pliocene) (Scillato-Yané 1982, Quiñones et al. 2019); San Luis Province: Río Quinto Formation (Late Miocene) (Strasser et al. 1998, Chiesa et al. 2019) (see Fig. 1). Amended diagnosis: The same as the genus by monotype. Descriptions and comparisons Skull: Descriptions are based on the specimen FMNH-P14360 (Fig. 3), an almost complete skull that includes the complete dental series, and the specimen FMNH-P15435 represented by a posterior fragment of skull that includes the distal ending of the palatine and the two last molariforms. The skull is elongated and larger than that of any extant Euphractinae, but considerably smaller (c. 10 cm) than that of the extinct Macroeuphractus. In dorsal view (Fig. 3A), nasal bones widen toward the nasal aperture, resulting in a broad rostral region. This aspect is also observed, even more exacerbated, in Macroeuphractus, but not in other euphractines. The nasal aperture has a dorsoventrally compressed oval outline. The nasal bones are not projected over the nasal aperture, differing from most euphractines, including Macroeuphractus and Euphractus. The frontal bones are anteriorly projected between the maxillary and nasal bones with an arrow-point morphology, as in other euphractines such as Euphractus and Chaetophractus, while they are barely projected in non-euphractine armadillos. At the level of the anterior zygomatic process, there are two olfactory bulbs, much more developed than in Macroeuphractus and extant euphractines. The preserved part of the zygomatic processes infers a large and broad orbit, as occurs in other large-sized armadillos, such as Macroeuphractus and Vetelia, and the major orbital constraint is closer to the anterior zygomatic process. The cranial case is mostly flattened. The suture between the frontal and parietal bones is mostly straight, and the suture between parietals rises as an elevated sagittal crest. This represents a rare character among armadillos, only shared with Macroeuphractus outesi, in which the sagittal crest is wider but lower than in M. scalabrinii. In each parietal, there is a line of large neurovascular foramina extending parallel to the sagittal crest. The sagittal crest extends posteriorly until joining a thick nuchal crest, which is W-shaped as occurs in most Euphractinae, such as Euphractus and Macroeuphractus. The sutures between parietal and temporal bones are poorly defined, as in Euphractus and Macroeuphractus, while in other euphractines (i.e. Chaetophractus and Zaedyus) they are well defined. The temporal fossa is enlarged, due to the posterior extent of the zygomatic squamosal process and a posterodorsal expansion of the parietals. The anteroposterior length of the parietals is approximately similar to that of the frontals; in extant euphractines the frontals are longer than the parietals, while in Macroeuphractus the parietals are longer than the frontal bones. The surface of the parietal area is rugose due to a series of scars for muscle attachment, which are far more developed than those of Euphractus, though not as much as those of Macroeuphractus. In lateral view (Fig. 3B), the skull profile is mostly straight with a subtle downward inclination of the rostral region as occurs in Macroeuphractus, while in most euphractines it has a sigmoidal profile (i.e. Zaedyus) or a flat cranial case with a marked downward inclined rostral region (i.e. Euphractus). The premaxillary bones are less vertically expanded than in Macroeuphractus, conferring a sharp appearance to the rostral region, similar to Euphractus. The infraorbital foramen is placed right at the basis of the anterior zygomatic process, a common character in Euphractinae, while in Tolypeutinae and Dasypodidae this foramen is placed in a more proximal position. The anterior root of the zygomatic process is robust and not laterally compressed as in Macroeuphractus. The lacrimal is dorsoventrally extended, as in Macrouphractus and Euphractus, while in other euphractines (i.e. Chaetophractus) it is much reduced. The posterior root is also robust, and the squamosal process of the zygomatic is nearly horizontal, as in Macroeuphractus, while in Euphractus it is oriented downwards. Below the posterior root, the external auditory meatus is proportionately larger than in extant euphractines, resembling that of Macroeuphractus. Viewed ventrally (Fig. 3C), the infraorbital foramen and the root of the anterior zygomatic process are placed at the level of the Mf6, as in Macroeuphractus and Euphractus. The palatal suture of the maxillary bones is mostly flat, while the suture of the palatines generates a slight crest, much less elevated than that of Macroeuphractus. The palatines are a bit more posteriorly extended than in Macroeuphractus, so that the choanae aperture is placed closer to the posterior zygomatic process, as occurs in Euphractus. The choanae aperture is concave and anteriorly projected, as in Macroeuphractus, while in extant euphractines it is triangular-shaped. The entopterygoid crests slightly deviate towards the external side as they distally extend, unlike in Macroeuphractus and Euphractus, in which they are straight. The ectotympanic and entotympanic are fused composing an ossified auditory bulla, which is proportionally larger than that of Macroeuphractus. The surface of the basioccipital is mostly flat, as in Euphractus and unlike in Macroeuphractus, which has a marked anteroposterior crest. The foramen magnum has a rounded outline and is little ventrally extended, differing from Macroeuphractus and Euphractus in which it has a triangular outline and is much expanded in ventral view. The occipital condyles have a similar inclined orientat