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| Lusovenator santosi
Malafaia, Mocho, Escaso & Ortega, 2020
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ABSTRACT
Carcharodontosaurian allosauroids were temporally restricted to the Cretaceous, being known from all land masses with the exception of Antarctica. In addition to Veterupristisaurus from Tanzania, exceptions to this distribution have been reported recently, consisting on fragmentary materials from Upper Jurassic strata of China, Germany, and Portugal. Here, we propose a new Late Jurassic carcharodontosaurian taxon, Lusovenator santosi, gen. et sp. nov. based on the reevaluation of previously described specimens from the Lusitanian Basin, Portugal. The performed phylogenetic analysis recovered Lusovenator santosi as an early branching carcharodontosaurian allosauroid diagnosed by an exclusive combination of characters, including three autapomorphic features: (1) large recesses in neural arch of anterior dorsal vertebrae; (2) well-developed and continuous longitudinal laminae extending from the tip of the prezygapophyses to the distal end of the postzygapophyses in mid-caudal vertebrae; and (3) supraacetabular crest of ilium forming a prominent ventrolaterally projecting shelf. Lusovenator santosi is the oldest carcharodontosaurian allosauroid yet discovered from Laurasia and supports unequivocally the hypothesis of a pre-Cretaceous scenario for the radiation of the clade. The identification of this taxon highlights the high diversity of medium- to large-bodied theropods in the later part of the Late Jurassic of the Iberian Peninsula. Carcharodontosauria is not yet known in correlative levels of the North American Morrison Formation, and the existence of contacts after the late Tithonian between these landmasses could explain the distribution of this clade and other dinosaur groups present in the Iberian Jurassic and in the North American Lower Cretaceous.
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| FIGURE 1. Lusovenator santosi, gen. et sp. nov., SHN.036, holotype, selected skeletal remains. A, odontoid and atlantal intercentrum in anterior view. B, cervical vertebra in right lateral view. C, D, anterior dorsal vertebra in C, right lateral and D, ventral views. E, sacral neural arch in posterior view. F, neural arch of anterior caudal vertebra in left lateral view. G, H, middle caudal vertebra in G, dorsal and H, left lateral views. I, right ilium in lateral view; J, K, pubes in J, left lateral and K, ventral views. L, silhouette showing preserved elements of SHN.036. A plus sign (+) indicates a diagnostic character and an asterisk (*) indicates an autapomorphy of Lusovenator santosi, gen. et sp. nov.
Abbreviations: acdl, anterior centrodiapophyseal lamina; act, acetabulum; at in, atlantal intercentrum; bf, brevis fossa; cpf, cupedicus fossa; isp, ischial peduncle; mec, medial crest; ms, medial symphysis; ncs, neurocentral suture; ns, neural spine; od, odontoid; pcdl, posterior centrodiapophyseal lamina; posdf, postzygapophyseal spinodiapophyseal fossa; poz, postzygapophysis; pp, parapophysis; prz, prezygapophysis; pup, pubic peduncle; spof, spinopostzygapophyseal fossa; tp, transverse process. Scale bars equal 25 mm (A), 50 mm (B–H), 100 mm (I–K), and 1 m (L).
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SYSTEMATIC PALEONTOLOGY
THEROPODA Marsh, 1881
TETANURAE Gauthier, 1986
AVETHEROPODA Paul, 1988
ALLOSAUROIDEA Marsh, 1878
CARCHARODONTOSAURIA Benson, Carrano, and
Brusatte, 2010
LUSOVENATOR SANTOSI, gen. et sp. nov.
Etymology— The generic name is composed from the Latin
words Luso, referring to Lusitania, the province in Roman Hispania related to the current Portugal, and venator, from the Latin
word for hunter; the specific name santosi after José Joaquim
dos Santos, who found and collected the holotype.
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| FIGURE 3. Time-calibrated evolutionary tree for Allosauroidea. Agreement subtree produced in TNT, with additional taxa incorporated (Veterupristisaurus milneri) marked with dashed line (see Fig. S1 for the full version of this tree). The pie charts represent relative frequencies of the clades in different paleogeographic areas calculated based on the number of taxa known in each area. Silhouette of dinosaur modified from the drawing of Scott Hartman. Global paleogeographic reconstructions modified from maps in Blakey (2019). |
CONCLUSION:
A new carcharodontosaurian theropod, Lusovenator santosi, gen.
et sp. nov., is defined based on a partial skeleton of a juvenile individual, SHN.036, collected in upper Kimmeridgian levels of the Lusitanian Basin. A second specimen, SHN.019, corresponding to some
axial and appendicular elements of a large-sized individual, from
upper Tithonian strata in the same geographic area, is tentatively
proposed as referred material. Also, an isolated femur previously
tentatively assigned to Lourinhanosaurus antunesi is interpreted
as belonging to a carcharodontosaur. Thus, the fossil record of
these allosauroids in the Lusitanian Basin spans from the Kimmeridgian to the upper Tithonian. Lusovenator santosi represents the
oldest member of Carcharodontosauria defined in the Upper Jurassic of Laurasia and extends the record of this clade, which was
already represented in the Lower Cretaceous of Europe. Despite
the great similarity in the theropod faunal composition, the recognition of a carcharodontosaurian allosauroid taxon provides a component of the Upper Jurassic Lusitanian Basin distinct from its
contemporaneous Morrison Formation in North America. The
development of a terrestrial dispersal route connecting these landmasses after the late Tithonian could explain the absence of Carcharodontosauria in the diverse theropod faunas of the Morrison
Formation and, additionally, their presence during the Early and
Late Cretaceous of North America. The new carcharodontosaurian
theropod provides the first evidence for sympatry among allosauroid theropods in the Late Jurassic of Europe. Additionally, the discovery of L. santosi sheds light on a poorly known period of
carcharodontosaurian history and adds important data to the knowledge of the early evolution of these allosauroids.
Elisabete Malafaia, Pedro Mocho, Fernando Escaso and Francisco Ortega. 2020. A New Carcharodontosaurian Theropod from the Lusitanian Basin: Evidence of Allosauroid Sympatry in the European Late Jurassic. Journal of Vertebrate Paleontology. e1768106. DOI: 10.1080/02724634.2020.1768106
