Saturday, November 4, 2017

[Paleontology • 2017] Mierasaurus bobyoungi • Descendants of the Jurassic Turiasaurs from Iberia Found Refuge in the Early Cretaceous of western USA

Mierasaurus bobyoungi 
Royo-Torres, Upchurch, Kirkland, DeBlieux, Foster, Cobos & Alcalá, 2017

reconstruction: Mike Skrepnick

A new, largely complete eusauropod dinosaur with cranial and postcranial elements from two skeletons, Mierasaurus bobyoungi gen. nov., sp. nov. from the lower Yellow Cat Member (Early Cretaceous) of Utah (USA), is the first recognized member of Turiasauria from North America. Moreover, according to our phylogenetic results, Moabosaurus utahensis from the lower Yellow Cat Member of Utah (USA) is also a member of this clade. This group of non-neosauropod eusauropods, which now includes five genera (Losillasaurus, Turiasaurus, Mierasaurus, Moabosaurus and Zby), was previously known only from the Jurassic of Europe. These recent discoveries in Utah suggest that turiasaurs as a lineage survived the Jurassic-Cretaceous extinction boundary and expanded their known range, at least, into western North America. The revised spatiotemporal distribution of turiasaurs is consistent with the presence of a land connection between North America and Europe sometime during the late Tithonian to Valanginian (c.147-133 Ma). Mierasaurus and Moabosaurus are the only non-neosauropod eusauropods known from North America, despite being younger than the classic neosauropods of the Morrison Formation (c.150 Ma).

Figure 2: The skull material (UMNH.VP.26004) of Mierasaurus bobyoungi gen. nov, sp. nov.

Systematic Palaeontology

Dinosauria Owen, 1842
Saurischia Seeley, 1887

Sauropoda Marsh, 1878
Eusauropoda Upchurch, 1995
Turiasauria Royo-Torres, Cobos and Alcalá, 2006

Mierasaurus bobyoungi gen. nov., sp. nov.

Etymology: Genus named for Bernardo de Miera y Pacheco, Spanish cartographer and chief scientist for the 1776 Domínguez-Escalante Expedition: the first European scientist to enter what is now Utah. The species name acknowledges the importance of the underappreciated research by Robert Young on the Early Cretaceous of Utah.

Holotype: A partial skeleton of a single individual (UMNH.VP.26004), comprising disarticulated cranial and postcranial elements from the type site (Doelling’s Bowl). We regard this as subadult because it is a relatively large animal with unfused vertebral centra and neural arches in some dorsal vertebrae. This individual includes a partial skull and jaw, teeth, atlas, 8 cervical vertebrae, 11 cervical ribs, 11 dorsal vertebrae, 6 dorsal ribs, 6 sacral ribs, 15 caudal vertebrae, two chevrons, right scapula and partial left scapula, left radius, left ulna, left manus, complete pelvic elements, both femora, left tibia, left fibula, left astragalus and left pes.

tibia, fibula and complete left hind foot of Mierasaurus bobyoungi.

Type locality and horizon: All Mierasaurus remains discussed herein are from Doelling’s Bowl bonebed, UMNH VP.LOC.1208 (Utah Loc. 42Gr0300v) within the lower Yellow Cat Member (below the marker calcrete), Cedar Mountain Formation, on lands managed by the U.S. Bureau of Land Management in northern Grand County, east-central Utah. In a preliminary report in a conference abstract, detrital zircon dating indicates maximum ages ranging from ~136.4 ± 1.1 Ma and ~132 Ma for lower Yellow Cat Member and ~137.2 ± 2.0 Ma for upper Yellow Cat Member. The combination of these data with the upper Berriasian-Valanginian age based on ostracods and charophyte fauna for the upper Yellow Cat Member indicates a conflict in the maximum age traditionally considered for it 124.2 ± 2.6 Ma (see Supplementary Information). All of these data suggest a potential age of late Berriasian-early Aptian (c.142-124 Ma) for the Yellow Cat Member.

Doelling’s Bowl has produced the iguanodont cf. Iguanocolossus sp., a new species of polacanthid ankylosaur, a large allosauroid theropod (teeth), and the dromaeosaur Yurgovuchia doellingi. Exact locality information will be provided to qualified researchers on request through the Natural History Museum of Utah or the Utah Geological Survey.

Diagnosis: A turiasaurian sauropod possessing the following features (autapomorphies marked by *): *the otosphenoidal ridge extends from the anterior surface of the paroccipital process, near its ventral margin and is restricted to the medialmost part of the latter process (Fig. 2b); *the occipital condyle has a pair of rounded ridges extending dorsoventrally, one on either lateral face of the condylar articular surface (Fig. 2a–d); *the atlantal intercentrum (Fig. 3e,f) bears a pair of depressions in the medial surface, facing posteromedially, each of which receives the anterolateral margin of the odontoid process; a well-developed spinoprezygapophyseal lamina extends anteriorly (Fig. 3a–d, g–m) as a low ridge onto the lateral surface of the prezygapophyses roofing a lateral fossa on prezygapophyses in middle and posterior cervical vertebrae (shared with the diplodocine Kaatedocus26); *cervical ribs bear a ridge or bulge on the lateral surface of the tuberculum, immediately posterior to the base of the anterior process (Fig. 3n–v); dorsal neural arches lack posterior centroparapophyseal laminae; *lateral depression on the distal ramus of haemal arches (Fig. 5g,h); metacarpal I longer than metacarpal IV, shared with Macronaria27 (Fig. 5m); a very short ischium compared to pubis length (ischium:pubis length ratio = 0.75) (Fig. 5d–f); the midpoint of the fourth trochanter placed in the proximal part of the femur (Fig. 5a); femur with subequal distal condyles (Fig. 5k); and pedal unguals 2 and 3 compressed dorsoventrally (Fig. 5l,o).

Figure 6: Phylogenetic relationships of Turiasauria: The time-calibrated phylogenetic relationships of Mierasaurus bobyoungi n. gen. et sp. nov. The box next to each taxon demarcates its temporal range, whereas the colour of the box reflects the continent(s) where the taxon occurs (yellow = South America, light blue = Asia, orange = North America; green = Europe, dark blue = Africa; black = several continents).

 mired Mierasaurus type specimen.

reconstruction: Mike Skrepnick 

Rafael Royo-Torres, Paul Upchurch, James I. Kirkland, Donald D. DeBlieux, John R. Foster, Alberto Cobos & Luis Alcalá. 2017. Descendants of the Jurassic Turiasaurs from Iberia Found Refuge in the Early Cretaceous of western USA.  Scientific Reports. 7, Article number: 14311. DOI: 10.1038/s41598-017-14677-2

Identificado un nuevo #dinosaurio de #Utah (#EEUU) con orígenes en #Teruel (#España)