Manidens

The type species of Manidens, Manidens condorensis, was described in the journal Naturwissenschaften in 2011. Manidens was named in by Diego Pol, Oliver Rauhut and Marcos Becerra. The generic name is derived from Latin manus, "hand", and dens, "tooth", a reference to the hand-shaped form of the posterior lower teeth. The specific name refers to the village of Cerro Cóndor, located near to the Queso Rallado site where the specimen was found by zoologist Guillermo Rougier. == Description ==

The holotype specimen of Manidens, MPEF-PV 3211, consists of a partial skeleton with a skull and lower jaw, including the axial column except most of the tail; a left shoulder girdle; and the pelvis. The specimens MPEF-PV 1719, 1786, 1718, 3810, 3811, isolated posterior teeth, from the same locality and horizon as the holotype specimen are also referred to this genus. MPEF-PV 3211 consists of 11 partially articulated fragments from a single individual, with several specimens separated: the right quadrate (MPEF-PV 3211-5), right quadratojugal (MPEF-PV 3211-6), right postorbital (MPEF-PV 3211-7), a complete pelvic girdle and sacral region with six sacral vertebrae (MPEF-PV 3211-1), one cervical vertebra (MPEF-PV 3211-8), two dorsal vertebrae (MPEF-PV 3211-2 and MPEF-PV 3211-4), and a caudal vertebra (MPEF-PV 3211-3). Some bones could not be fully separated due to overlapping and were left in three blocks of associated remains (MPEF-PV 3211-9, MPEF-PV 3211-10, and MPEF-PV 3211-11). Other specimens include partial articulated specimens, skull & associated elements as well referred isolated teeth: MPEF-PV 3809, MPEF-PV 3808, MPEF-PV 10867, MPEF-PV 1719, MPEF-PV 1786, MPEF-PV 1718, MPEF-PV 3810, MPEF-PV 3811, MPEF-PV 3812, MPEF-PV 3813, MPEF-PV 3814, MPEF-PV 3815, MPEF-PV 3816, MPEF-PV 10866. The cervical vertebrae are shorter than the dorsal vertebrae and feature short, stout diapophyses and parapophyses, with the anterior cervical having strongly elongated, hypertrophied epipophyses, similar to those in Heterodontosaurus. Manidens was a relatively basal heterodontosaurid that grew to about in length and in body mass, smaller than later heterodontosaurids. It has high-crowned teeth indicative of an increased adaptation to a herbivorous diet but lacks the wear facets seen in more advanced forms like Heterodontosaurus. Manidens is the sister taxon of a clade consisting of the African species Heterodontosaurus, Abrictosaurus and Lycorhinus, indicating an early radiation of the heterodontosaurids. Skull Several Autapomorphies were identified, including postorbital has a tubercle-like thickening at the base of the jugal process, positioned between the orbit and the lowest part of the postorbital fossa, oriented dorsoventrally, jugal process of the postorbital reaches the main body of the jugal, with the jugal contributing minimally to the posterior orbit boundary. The coronoid has a triangular posterior process extending further back than the coronoid process of the dentary with the anterior foramen of the surangular featuring a wide, anteriorly developed fossa that becomes fusiform posterior to the foramen. Postcranea The postcranial skeleton of Manidens includes elements from the vertebral column, ribs, girdles, and limited appendicular bones. The axial series features completely fused neurocentral junctions in all preserved vertebrae, indicating an advanced growth stage. Cervical vertebrae are relatively short with robust processes for rib attachment, including distinctive proatlases (first reported in heterodontosaurids) that articulate with the skull base. Dorsal vertebrae are longer and barrel-shaped, with varying transverse process lengths and neural spine heights that increase posteriorly in some positions, accompanied by slender, curved thoracic ribs. The sacrum consists of six fully fused vertebrae, with extensive fusion of centra, zygapophyses, and most neural spines, supported by robust sacral ribs that anchor to the ilium; ossified tendons are present along the sacral region, likely providing dorsal stiffening. Caudal vertebrae show elongated centra in anterior positions, with prominent transverse processes and facets for chevrons, transitioning to shorter processes further back. The pectoral girdle comprises a fused scapulocoracoid with a straight to gently curved scapular blade, a modest acromion ridge, and a plate-like coracoid featuring a hooked posteroventral process and a centrally placed foramen. The pelvic girdle is well-developed, with an elongated ilium having a prominent, ventrally deflected preacetabular process (about 42% of total length), a fully open acetabulum lacking a medial shelf, distinct muscle scars including a bony antitrochanter on the ischial peduncle, and a shorter postacetabular process with a narrow brevis shelf. The opisthopubic pubis includes a short prepubic element and a slender postpubic rod, while the ischium has a straight shaft with a longitudinal groove for muscle attachment and contributes to an elongated obturator foramen. Scattered appendicular remains include a probable pedal phalanx from the fourth digit and a flattened proximal carpal bone. Rib histology reveals poorly vascularized parallel-fibred bone with minimal remodeling and no growth interruptions, consistent with sustained but moderate growth rates. Overall, these features align Manidens closely with other heterodontosaurids while showing unique traits in sacral fusion and girdle proportions. Phylogeny Cladogram after Pol et al., 2011: }} • Note: Pol et al. regard Echinodon as a genus of Heterodontosauridae. == Paleoecology ==

'') The holotype of Manidens comes from the Chacritas Member of the Cañadón Asfalto Formation. This member is mostly made of two major depositional settings: lacustrine and fluvial deposits, that have intervals of tuffaceous materials, suggesting this environments coevolved with volcanic activity. Palustrine littoral environments levels are seen at Cerro Cóndor and Estancia Fossati, characterized by the presence of lacustrine limestones interbedded with shales, tuffs and sandstones. The lacustrine section has been called the "Chacritas Paleolake", and seems to have been a rather saline or even hypersaline hydrologically closed pan lake, shallow in deep, with marginal zones and palustrine subenvironments made of low-energy ramp-like margins. Fossils attributed to Manidens from Argentina indicate that this dinosaur may have been at least partially arboreal. The specimens consists of a series of bones from both hind feet and a few tail vertebrae, and are tentatively attributed to Manidens on the basis of provenance. The long toe bones indicate that the toe bones were capable of grasping; distinct anchor attachments for the muscles and tendons of the hallux indicate that its hallux was smaller than the rest of the toes but could still have grasped. Principal component analysis found that the feet of Manidens were most similar to those of tree-perching birds. Based on the unusual morphology of its teeth, it has been speculated that Manidens may have been partially carnivorous, as has occasionally been suggested for heterodontosaurids. == References ==