[Paleontology • 2018] Semi-aquatic Adaptations in A Spinosaur from the Lower Cretaceous of Brazil

A Spinosaurinae at the Aptian-Albian lagunar/shallow marine environment of the Romualdo Formation, Araripe Basin, NE Brazil.

in Aureliano, Ghilardi, Buck, et al., 2018. 

DOI: 10.1016/j.cretres.2018.04.024 

Illustration by Julio Lacerda.

Highlights

• Spinosaur histology is here described for the first time.

• Extreme bone compactness (osteosclerosis) was present in Brazilian Spinosaurinae.

• These modifications appeared millions of years before the Moroccan Spinosaurus.

• One of the largest spinosaur specimens from the Early Cretaceous of South America.

Abstract

Spinosaurinae are known to have a strong relationship with aquatic environments, involving several anatomical adaptations. Nonetheless, this group of theropods remains enigmatic, due to the relative incompleteness of its fossil record. A large partial tibia from the Aptian-Albian Romualdo Formation, Northeast Brazil, is herein described through anatomical comparisons and paleohistological analyzes. It features characteristics previously only observed in Spinosaurus aegyptiacus, which includes a reduced fibular crest and an osteosclerotic condition. The later, a character supported as correlated with semi-aquatic habits in many limbed vertebrates. The results presented here support high bone compactness being already present in Brazilian Spinosaurinae millions of years before the Moroccan Spinosaurus. Furthermore, histological analyses demonstrate the Romualdo Formation specimen was a young subadult still growing fast by the time of its death, and suggests Araripe Basin Spinosaurinae could have grown larger than previously thought. This work contributes to a better paleobiological and ecological understanding of South American spinosaurs, and helps fill a gap in the macroevolutionary comprehension of Spinosaurinae. Ultimately, it also contributes to further advancing the paleoecological characterization of the Romualdo Formation.

Keywords: Paleohistology; Araripe basin; Theropoda; Megalosauroidea; Spinosaurinae

Systematic paleontology

Dinosauria Owen, 1842

Theropoda Marsh, 1882

Tetanurae Gauthier, 1986

Megalosauroidea Fitzinger, 1843

Spinosauridae Stromer 1915

Spinosaurinae Stromer, 1915

gen. et. sp. indet.

Referred material: LPP-PV-0042, a fragmentary tibia.

Locality and horizon: Exact geological and geographical provenance is unknown, but the fossil was collected in the Araripe area, Northeast Brazil. Outcrops of the Lower Cretaceous Santana Group (Araripe Basin) are worldwide known for providing well-preserved fossils and are located in the Araripe region. 

Fig. 6. 1. Spinosaurinae remains currently recovered from the Romualdo Formation, Araripe Basin, Brazil. Not to scale.
 A, USP GP/2T-5, holotype of Angaturama limai ( Kellner & Campos, 1996), fragmentary anterior tip of skull.
B, SMNS 58022, holotype of Irritator challengeri (Sues et al., 2002) (originally mistakenly identified as a maniraptor by Martill et al., 1996), partial posterior portion of skull and mandible.
C, MN 4743-V, incomplete indeterminate spinosaur sacral and caudal vertebrae series (S3, S4, S5, C1, C2. C3, C4, C4, C6) (Bittencourt & Kellner, 2004).
D, MN 7021-V, indeterminate spinosaur rib (Machado & Kellner, 2007). E, MN4819-V, incomplete indeterminate spinosaur pubis, pelvis, dorsal, sacral and caudal vertebrae (d, S1, S2, S3, S4, S5, C1), incomplete indeterminate spinosaur right manus, fragmentary right tibia and femur ( Machado et al., 2008; Machado and Kellner, 2009 ; Machado, 2010).
 F, LPP-PV-0042, Spinosaurinae indet. metaphysis of left tibia described in this work. Skeletal reconstruction made by Tito Aureliano, based on the work by Scott Hartman and Marcos Sales. 

2. Romualdo Spinosaurinae specimens to scale. A, Angaturama USP GP/2T (∼8.3 m, on the reconstruction by Sales & Schultz, 2017). B, Irritator SMNS 58022 (∼6.5 m, from the reconstruction by Sales & Schultz, 2017). C, Spinosaurinae indet. MN4819-V (∼5.9 m; Machado et al., 2008). D, Spinosaurinae indet. LPP-PV-0042 (∼10 m; this work). Scale bar in 7.2 is 1 m. 

Fig. 8. Reconstruction of a Spinosaurinae at the Aptian-Albian lagunar/shallow marine environment of the Romualdo Formation, Araripe Basin, NE Brazil. 

Illustration by Julio Lacerda.

Fig. 7. Inferred food web of the Aptian-Albian Romualdo Formation, Northeast Brazil. Vertebrate silhouettes are highlighted in black. Trophic relations are represented by arrows, of which solid bold red represent ecological interactions with direct fossil evidence from Romualdo Formation; solid black indicate putative trophic interactions with general theoretical support; and dashed grey represent weak or uncertain but plausible trophic links.
1, Spinosaurinae; 2, small to medium sized terrestrial theropods; 3, pterosaurs; 4, semi-aquatic crocodyliforms; 5, terrestrial omnivorous crocodyliforms; 6, semi-aquatic chelonians; 7, large fishes; 8, small fishes; 9, plants; 10, macroinvertebrates; 11, plankton. See Text S1 in the Supplementary material for list of references. Spinosaurinae silhouette by Tito Aureliano. Other silhouettes from Phylopic (http://phylopic.org/), courtesy of Almandine (vectorized by T. Michael Keesey), FunkMonk (adapted), Hans Hillewaert, John Conway, Melissa Broussard, Nobu Tamura (vectorized by T. Michael Keesey), Olegivvit, Robert Gay and Sergio A. Muñoz-Gómez.  

Conclusion: 

The Romualdo Formation specimen LPP-PV-0042 comprises a fragmentary tibia with a reduced fibular crest and osteosclerotic histology previously only observed in Spinosaurus aegyptiacus, supporting that this unique feature was already present in Brazilian Spinosaurinae (basal Spinosaurinae) during the Aptian-Albian time, at least 10 myr before the Moroccan Spinosaurus.

Histological analyses suggest LPP-PV-0042 was a young, fast growing subadult and also that the bone microstructure varies a lot across the cross-section, probably due to areas of muscle insertion. The latter observation suggests that caution is needed when describing bone histology of dinosaurs, since only one slice from the shaft is not always representative of the entire histology of the bone.

Furthermore, the current specimen represents one of the largest spinosaurs from this unit so far (∼10 m in reconstructed TL). It was larger than the Irritator holotype and possibly larger than Angaturama holotype as well. Considering the subadult status inferred from its histology, the referred individual would have grown even larger.

The Romualdo paleoenvironment could support large predators with semi-aquatic habits due to its high productivity and diversity of aquatic species as an ecotone. Spinosaurinae from Romualdo Formation probable occupied the position of apex predators different.

Thus, the skeletal element LPP-PV-0042 from the Romualdo Formation, although fragmentary, has provided much information about Brazilian Spinosaurinae paleobiology and ecology. Moreover, it gives new insight into the evolution of semi-aquatic adaptations in this group, revealing the need to investigate other taxa within the clade and expand the search for more spinosaur fossils.

  

Tito Aureliano, Aline M. Ghilardi, Pedro V. Buck, Matteo Fabbri, Adun Samathi, Rafael Delcourt, Marcelo A. Fernandes and Martin Sander. 2018. Semi-aquatic Adaptations in A Spinosaur from the Lower Cretaceous of Brazil. Cretaceous Research. In Press.  DOI: 10.1016/j.cretres.2018.04.024

 twitter.com/AlineGhilardi/status/992177606933000192

 twitter.com/AlineGhilardi/status/992152367633240065

Dense Bones and Other Aquatic Adaptations in Spinosaurs  https://blog.everythingdinosaur.co.uk/blog/_archives/2018/05/06/dense-bones-and-other-aquatic-adaptations-in-spinosaurs.html

[Paleontology • 2018] Tratayenia rosalesi • A New Megaraptoran Theropod Dinosaur from the Upper Cretaceous Bajo de la Carpa Formation of northwestern Patagonia

Tratayenia rosalesi 

Porfiri, Juárez Valieri, Santos & Lamanna, 2018

  DOI: 10.1016/j.cretres.2018.03.014 
Illustration: Andrew McAfee

Abstract

We describe Tratayenia rosalesi gen. et sp. nov., a new megaraptoran theropod dinosaur from the Upper Cretaceous of Patagonia, Argentina. The holotype consists of a well-preserved, mostly articulated series of dorsal and sacral vertebrae, two partial dorsal ribs, much of the right ilium, and pubis and ischium fragments. It was found in a horizon of the Upper Cretaceous (Santonian) Bajo de la Carpa Formation of the Neuquén Group in the Neuquén Basin exposed near the town of Añelo in Neuquén Province of northwestern Patagonia. Phylogenetic analysis recovers Tratayenia within the Gondwanan megaraptoran subclade Megaraptoridae. The new taxon exhibits similarities to other megaraptorids such as Aerosteon riocoloradensis, Megaraptor namunhuaiquii, and Murusraptor barrosaensis, but also presents differences in the architecture of the dorsal and sacral vertebrae and the morphology of the ilium. Tratayenia is the first megaraptoran that unequivocally preserves the complete sequence of sacral vertebrae, thereby increasing knowledge of the osteology of the clade. Moreover, depending on the chronostratigraphic ages of the stratigraphically controversial megaraptorids Aerosteon and Orkoraptor burkei, as well as the phylogenetic affinities of several fragmentary specimens, the new theropod may be the geologically youngest megaraptorid or megaraptoran yet discovered. Tratayenia is also the largest-bodied carnivorous tetrapod named from the Bajo de la Carpa Formation, reinforcing the hypothesis that megaraptorids were apex predators in southern South America from the Turonian through the Santonian or early Campanian, following the extinction of carcharodontosaurids.

Keywords: Theropoda; Megaraptora; Megaraptoridae; Bajo de la Carpa Formation; Upper Cretaceous; Patagonia; Argentina

Figure 3. Preserved dorsal vertebrae and sacrum of  Tratayenia rosalesi gen. et sp. nov. (MUCP v1162). A, left lateral view. B, right lateral view.

Figure 2. Tentatively reconstructed body silhouette of  Tratayenia rosalesi gen. et sp. nov. showing the bones preserved in the holotype (MUCP v1162). Body regions not preserved in Tratayenia are based primarily on corresponding elements of the following megaraptorid species: cranium (Megaraptor namunhuaiquii, Murusraptor barrosaensis), mandible (Australovenator wintonensis, M. barrosaensis), postcranial axial skeleton (Aerosteon riocoloradensis, M. namunhuaiquii), appendicular skeleton (A. riocoloradensis, A. wintonensis, M. namunhuaiquii). Scale bar equals 1 m.

Systematic paleontology

 Dinosauria Owen, 1842
 Theropoda Marsh, 1881
 Tetanurae Gauthier, 1986

 Megaraptora Benson, Carrano, and Brusatte, 2010
 Megaraptoridae Novas, Agnolín, Ezcurra, Porfiri, and Canale, 2013

 Tratayenia rosalesi gen. et sp. nov. 

Etymology. Genus name for Tratayén, the locality where the holotype was collected; species name in honor of Diego Rosales, the discoverer of the specimen. 

....

Conclusions: 

Tratayenia rosalesi is a new taxon of megaraptoran theropod, the first to be described from the Santonian Bajo de la Carpa Formation of the Neuquén Group. Its discovery constitutes a previously unreported stratigraphic occurrence in the megaraptorid fossil record of northern Patagonia. The elevated pneumaticity and morphological resemblance of the axial and pelvic elements of Tratayenia to those of the megaraptorids Aerosteon riocoloradensis and Murusraptor barrosaensis suggests 851 particularly close relationships between these three taxa. Nevertheless, Tratayenia also exhibits a number of unique morphologies that justify the erection of a new taxon. The holotype is the first megaraptoran specimen to preserve a nearly complete sequence of middle and posterior dorsal vertebrae and the complete sacrum, which augments knowledge of serial variation in this area of the axial skeleton. Tratayenia rosalesi is the largest carnivorous taxon known from the Bajo de la Carpa Formation, and, like other Patagonian megaraptorids, was likely the apex predator in its paleoecosystem. 

Juan D. Porfiri, Rubén D. Juárez Valieri, Domenica D.D. Santos and Matthew C. Lamanna. 2018. A New Megaraptoran Theropod Dinosaur from the Upper Cretaceous Bajo de la Carpa Formation of northwestern Patagonia. Cretaceous Research. In Press.  DOI: 10.1016/j.cretres.2018.03.014

 researchgate.net/publication/323878344_A_new_megaraptoran_theropod_dinosaur_from_the_Upper_Cretaceous_Bajo_de_la_Carpa_Formation_of_northwestern_Patagonia

https://carnegiemnh.org/press/new-patagonian-predator-sheds-light-on-mysterious-meat-eating-dinosaur-group/

  

[Paleontology • 2017] A Dinosaur Missing-Link? Chilesaurus and the Early Evolution of Ornithischian Dinosaurs

Chilesaurus diegosuarezi 

Novas, Salgado, Suárez, Agnolín, Ezcurra, Chimento, de la Cruz, Isasi, Vargas & Rubilar-Rogers, 2015

DOI: 10.1098/rsbl.2017.0220  & DOI: 10.1038/nature14307

Illustration: Gabriel Lío

Abstract

The enigmatic dinosaur taxon Chilesaurus diegosuarezi was originally described as a tetanuran theropod, but this species possesses a highly unusual combination of features that could provide evidence of alternative phylogenetic positions within the clade. In order to test the relationships of Chilesaurus, we added it to a new dataset of early dinosaurs and other dinosauromorphs. Our analyses recover Chilesaurus in a novel position, as the earliest diverging member of Ornithischia, rather than a tetanuran theropod. The basal position of Chilesaurus within the clade and its suite of anatomical characters suggest that it might represent a ‘transitional’ taxon, bridging the morphological gap between Theropoda and Ornithischia, thereby offering potential insights into the earliest stages of ornithischian evolution, which were previously obscure. For example, our results suggest that pubic retroversion occurred prior to some of the craniodental and postcranial modifications that previously diagnosed the clade (e.g. the presence of a predentary bone and ossified tendons).

KEYWORDS: Archosauria, Dinosauria, Ornithischia, systematics: phylogeny, Jurassic

Figure 2. Ornithischian features of Chilesaurus. (a) Simplified tree with key acquisitions marked on;
(b) right dentary of Chilesaurus (SNGM-1935) in lateral view; (c) right dentary of Heterodontosaurus (SAM-PK-K1332) in lateral view; (d) pelvic girdle of Chilesaurus SNGM-1936 in lateral view; (e) pelvic girdle of Agilisaurus (ZDM T6011) in lateral view; (f) right femur of Chilesaurus (SNGM-1935) in anterior view; (g) right tibia and fibula of Chilesaurus (SNGM-1935) in posterior view.

Numbers indicate the acquisition of key ornithischian synapomorphies within the clade: 1, complete loss of recurvature in maxillary and dentary teeth; 2, edentulous anterior end of the dentary; 3, predentary bone at the anterior end of the lower jaw; 4, retroversion of the pubis; 5, rod-like pubic shaft; 6, pubic symphysis restricted to the distal end; 7, anteriorly elongate preacetabular process; 8, broadened, wing-like anterior trochanter; 9, fibula less than half the width of the tibia at midshaft. Dark grey circles denote unknown in Pisanosaurus.

Conclusion: 

This study identifies Chilesaurus as a transitional ornithischian taxon and suggests that the unique suite of anatomical features it possesses could be informative not only in unravelling dinosaur interrelationships, but also in shedding light on the evolution of the anatomical peculiarities that characterize ornithischians. Paradoxically, this early diverging lineage is of Late Jurassic age, implying an extensive ghost lineage between it and other ornithischians and basal theropods. If this hypothesis is correct, this ghost lineage suggests that other similar animals await discovery in Late Triassic–Middle Jurassic deposits. This study highlights the importance of broad taxon sampling when attempting to assess the phylogenetic affinities of enigmatic taxa such as Chilesaurus and also demonstrates the utility of this new early dinosaur dataset for testing the relationships proposed for other problematic dinosauromorph taxa.

Matthew G. Baron and Paul M. Barrett. 2017. A Dinosaur Missing-Link? Chilesaurus and the Early Evolution of Ornithischian Dinosaurs. Biology Letters. 13(8); 20170220. DOI: 10.1098/rsbl.2017.0220.

Abstract: Many dinosaur skeletons show evidence of behavior, including feeding, predation, nesting, and parental care. The resting posture of the forelimbs has been studied in some theropod species, in relation to the acquisition of flight in advanced maniraptoran theropods. Chilesaurus diegosuarezi is a bizarre tetanuran recently described from the Toqui Formation (latest Tithonian) of southern Chile that is represented by multiple well-preserved and articulated specimens. The aim of the present work is to analyze the forelimb posture of four articulated specimens of Chilesaurus: SNGM-1935 (holotype), SNGM-1936, SNGM-1937, SNGM-1938; focusing on its anatomical description, and phylogenetic and behavioral implications. All the preserved specimens of Chilesaurus show strongly ventrally flexed arms with the hands oriented backwards, an arrangement that closely resembles those in dinosaur specimens previously described as preserving resting posture, such as Mei long, Sinornithoides youngi, and Albinykus baatar. As a result, it seems that individuals of Chilesaurus have been in passive activity (e.g. feeding, resting) when they were buried quickly, allowing their fossilization in life position and preserving the forelimb resting posture. The arrangement of the forelimb bones in Chilesaurus could show the first evidences of the structures linked to the muscles that flex the forearms, features related with the acquisition of flying control in advanced maniraptorans.

Nicolás R. Chimento, Federico L. Agnolin, Fernando E. Novas, Martín D. Ezcurra, Leonardo Salgado, Marcelo P. Isasi, Manuel Suárez, Rita De La Cruz, David Rubilar-Rogers and Alexander O. Vargas. 2017. Forelimb posture in Chilesaurus diegosuarezi (Dinosauria, Theropoda) and its behavioral and phylogenetic implications. Ameghiniana. in press. DOI: 10.5710/AMGH.11.06.2017.3088.

ResearchGate.net/publication/317546006_FORELIMB_POSTURE_IN_CHILESAURUS_DIEGOSUAREZI

Study identifies dinosaur ‘missing link’

cam.ac.uk/research/news/study-identifies-dinosaur-missing-link

Fernando E. Novas, Leonardo Salgado, Manuel Suárez, Federico L. Agnolín, Martín D. Ezcurra, Nicolás R. Chimento, Rita de la Cruz, Marcelo P. Isasi, Alexander O. Vargas and David Rubilar-Rogers. 2015. An Enigmatic Plant-eating Theropod from the Late Jurassic period of Chile. Nature. (2015) DOI: 10.1038/nature14307

[Paleontology • 2016] Murusraptor barrosaensis • A New Megaraptoran Dinosaur (Theropoda, Megaraptoridae) from the Late Cretaceous of Patagonia

Murusraptor barrosaensis  

Coria & Currie, 2016

  DOI: 10.1371/journal.pone.0157973 

Abstract

A skeleton discovered in the Upper Cretaceous Sierra Barrosa Formation (Turonian-Coniacian) of Neuquén Province, Argentina represents a new species of theropod dinosaur related to the long snouted, highly pneumatized Megaraptoridae. The holotype specimen of Murusraptor barrosaensis n.gen et n.sp. (MCF-PVPH-411) includes much of the skull, axial skeleton, pelvis and tibia. Murusraptor is unique in having several diagnostic features that include anterodorsal process of lacrimal longer than height of preorbital process, and a thick, shelf-like thickening on the lateral surface of surangular ventral to the groove between the anterior surangular foramen and the insert for the uppermost intramandibular process of the dentary. Other characteristic features of Murusraptor barrosaensis n.gen. et n. sp.include a large mandibular fenestra, distal ends of caudal neural spines laterally thickened into lateral knob-like processes, short ischia distally flattened and slightly expanded dorsoventrally. Murusraptor belongs to a Patagonian radiation of megaraptorids together with Aerosteon, Megaraptor and Orkoraptor. In spite being immature, it is a larger but more gracile animal than existing specimens of Megaraptor, and is comparable in size with Aerosteon and Orkoraptor. The controversial phylogeny of the Megaraptoridae as members of the Allosauroidea or a clade of Coelurosauria is considered analyzing two alternative data sets.

Systematic Paleontology

Dinosauria Owen, 1842

Theropoda Marsh, 1881

Tetanurae Gauthier, 1986

Megaraptora Benson, Carrano, Brusatte, 2010

Megaraptoridae Novas, Agnolin, Ezcurra, Porfiri, Canale 2013

Murusraptor barrosaensis new genus, new species

Etymology: “Murus” is a Latin term for “wall”, referring to the discovery of the specimen in the wall of a canyon; “barrosaensis” alludes to Sierra Barrosa, the locality where it was collected.

Holotype: Partial skeleton (Museo Carmen Funes MCF-PVPH-411) includes a complete braincase, lacrimal, prefrontal, postorbital, quadrate, pterygoid, ectopterygoid, teeth, twelve vertebrae, eleven thoracic ribs, one haemal arch, several gastralia, a manual ungual, complete left ilium, part of right ilium, proximal ends of the pubes, distal ends of the ischia, the right tibia, and a calcaneum (Fig 1).

Fig 1. A) Skull reconstruction of Murusraptor barrosaensis, MCF-PVPH-411. B) Body reconstruction

Both illustrations show recovered elements in white. Scale bars: A = 10 cm, B = 1 m.   DOI: 10.1371/journal.pone.0157973

Fig 3. Field photos of the excavation of MCF-PVPH-411 (Murusraptor barrosaensis).
A and B, the authors excavating the right ilium. C-F, different appendicular elements in their original burial positions before collection.

  DOI: 10.1371/journal.pone.0157973  

Diagnosis: Murusraptor barrosaensis is unique in having anterodorsal process of lacrimal longer than height of preorbital process, and a thick, shelf-like thickening on the lateral surface of surangular ventral to the groove between the anterior surangular foramen and the insert for the uppermost intramandibular process of the dentary. Two other characters are only known in Murusraptor; sacral ribs hollow and tubelike; short ischia distally flattened and slightly expanded dorsoventrally. These characters are equivocal because they are unknown in other members of the clade. Also, the following combination of diagnostic characters was obtained after running the phylogenetic analysis using TNT: Character 95, basipterygoid processes of the basisphenoid located anteroventrally, with basisphenoid recess opening posterodorsally (also present in coelophysids); Character 98, basisphenoid with a shallow embayment indentation between basal tubera and basipterygoid processes (also present in Cryolophosaurus and basal theropods); Character 216, rather straight chevrons (reversal to the plesiomorphic condition).

Rodolfo A. Coria and Philip J. Currie. 2016.  A New Megaraptoran Dinosaur (Dinosauria, Theropoda, Megaraptoridae) from the Late Cretaceous of Patagonia. PLoS ONE. 11(7): e0157973. DOI: 10.1371/journal.pone.0157973

Another Brick in the “Murus”: Meet the newest Megaraptoran theropod, Murusraptor http://blogs.plos.org/paleocomm/2016/07/20/another-brick-in-the-murus-meet-the-newest-megaraptoran-theropod-murusraptor

[Paleontology • 2016] Gualicho shinyae • An Unusual New Theropod with a Didactyl Manus from the Upper Cretaceous of Patagonia, Argentina

Gualicho shinyae 

Apesteguía, Smith, Valieri & Makovicky, 2016   DOI: 10.1371/journal.pone.0157793 

Abstract

Background

Late Cretaceous terrestrial strata of the Neuquén Basin, northern Patagonia, Argentina have yielded a rich fauna of dinosaurs and other vertebrates. The diversity of saurischian dinosaurs is particularly high, especially in the late Cenomanian-early Turonian Huincul Formation, which has yielded specimens of rebacchisaurid and titanosaurian sauropods, and abelisaurid and carcharodontosaurid theropods. Continued sampling is adding to the known vertebrate diversity of this unit.

Methodology/ Principal Findings

A new, partially articulated mid-sized theropod was found in rocks from the Huincul Formation. It exhibits a unique combination of traits that distinguish it from other known theropods justifying erection of a new taxon, Gualicho shinyae gen. et sp. nov. Gualicho possesses a didactyl manus with the third digit reduced to a metacarpal splint reminiscent of tyrannosaurids, but both phylogenetic and multivariate analyses indicate that didactyly is convergent in these groups. Derived characters of the scapula, femur, and fibula supports the new theropod as the sister taxon of the nearly coeval African theropod Deltadromeus and as a neovenatorid carcharodontosaurian. A number of these features are independently present in ceratosaurs, and Gualicho exhibits an unusual mosaic of ceratosaurian and tetanuran synapomorphies distributed throughout the skeleton.

Conclusions/ Significance

Gualicho shinyae gen. et sp. nov. increases the known theropod diversity of the Huincul Formation and also represents the first likely neovenatorid from this unit. It is the most basal tetatanuran to exhibit common patterns of digit III reduction that evolved independently in a number of other tetanuran lineages. A close relationship with Deltadromaeus from the Kem Kem beds of Niger adds to the already considerable biogeographic similarity between the Huincul Formation and coeval rock units in North Africa.

a pair of Gualicho dinosaurs pursuing prey.

illustration: Jorge Gonzalez and Pablo Lara 

Systematic paleontology

Dinosauria

Theropoda

Tetanurae

Avetheropoda

Gualicho shinyae gen. et sp. nov. 

(replaces Nototyrannus violantei Anonymous, 2011, nomen nudum)

Holotype: MPCN PV 0001, comprising four articulated centra from the dorsal vertebral column, an articulated gastral basket, a section of the tail distal to the transition point, the left scapulocoracoid and forelimb, the distal end of both pubes including the pubic boot, and parts of both hind limbs (Fig 1A). Much of the specimen had been lost to erosion when discovered, but the preserved parts including the forelimb, dorsal vertebrae, gastralia, and feet were articulated. Specimen measurements are provided in Table 1.

 Skeletal reconstruction of Gualicho shinyae showing recovered elements in white and missing elements in grey shading.

Artwork by J. González. 

Etymology: Gualicho, a Spanish name derived from the Gennaken (günün-a-künna or northern Tehuelche language) watsiltsüm, for a goddess who was considered the owner of animals and later, following the introduction of Christianity, reinterpreted as a demonic entity. She is now considered a source of misfortune by rural settlers (gauchos) of the Southern Cone. The name was chosen to reflect the difficult circumstances surrounding the discovery and study of the specimen, and its contentious history following excavation. The specific name honors Ms. Akiko Shinya, Chief Fossil Preparator at the Field Museum, for her many contributions to paleontology including discovery of the holotype of Gualicho on February 13th, 2007 (see S1 Fig).

Sebastián Apesteguía, Nathan D. Smith, Rubén Juárez Valieri and Peter J. Makovicky. 2016. An Unusual New Theropod with a Didactyl Manus from the Upper Cretaceous of Patagonia, Argentina. PLoS ONE. 11(7): e0157793.   DOI: 10.1371/journal.pone.0157793

Meet Gualicho shinyae, the puny-armed distant relative of T. rex https://www.theguardian.com/science/2016/jul/13/meet-gualicho-shinyae-the-puny-armed-distant-relative-of-t-rex

[Paleontology • 2016] Morphofunctional Analysis of the Quadrate of Spinosauridae (Dinosauria: Theropoda) and the Presence of Spinosaurus and a Second Spinosaurine Taxon in the Cenomanian of North Africa

two species of Spinosaurinae, and ascribed to Spinosaurus aegyptiacus and ?Sigilmassasaurus brevicollis from the Cenomanian of North Africa

Illustration: S. Krasovskiy atrox1.deviantart.com DOI:  10.1371/journal.pone.0144695

Abstract

Six quadrate bones, of which two almost certainly come from the Kem Kem beds (Cenomanian, Upper Cretaceous) of south-eastern Morocco, are determined to be from juvenile and adult individuals of Spinosaurinae based on phylogenetic, geometric morphometric, and phylogenetic morphometric analyses. Their morphology indicates two morphotypes evidencing the presence of two spinosaurine taxa ascribed to Spinosaurus aegyptiacus and ?Sigilmassasaurus brevicollis in the Cenomanian of North Africa, casting doubt on the accuracy of some recent skeletal reconstructions which may be based on elements from several distinct species. Morphofunctional analysis of the mandibular articulation of the quadrate has shown that the jaw mechanics was peculiar in Spinosauridae. In mature spinosaurids, the posterior parts of the two mandibular rami displaced laterally when the jaw was depressed due to a lateromedially oriented intercondylar sulcus of the quadrate. Such lateral movement of the mandibular ramus was possible due to a movable mandibular symphysis in spinosaurids, allowing the pharynx to be widened. Similar jaw mechanics also occur in some pterosaurs and living pelecanids which are both adapted to capture and swallow large prey items. Spinosauridae, which were engaged, at least partially, in a piscivorous lifestyle, were able to consume large fish and may have occasionally fed on other prey such as pterosaurs and juvenile dinosaurs.

Systematic Paleontology

Dinosauria Owen, 1842 

Saurischia Seeley, 1887 

Theropoda Marsh, 1881 

Tetanurae Gauthier, 1986 

Megalosauroidea (Fitzinger, 1843) Walker 1964 

Spinosauridae Stromer, 1915 

Spinosaurinae (Stromer, 1915) Sereno et al., 1998 

Description: The six isolated quadrates from the Kem Kem beds of Morocco clearly belong to two morphotypes (Figs 2–4) based on the size and outline of the quadrate foramen, shape of the mandibular articulation, and outline, surface, and orientation of the quadratojugal contacts. Measurements taken on each quadrate (Fig 5A–5D) are provided in Table 1.

Spinosaurus Stromer, 1915 

Spinosaurus aegyptiacus Stromer, 1915 

?Sigilmassasaurus Russel, 1996 

?Sigilmassasaurus brevicollis Russel, 1996 

Spinosaurus aegyptiacus and ?Sigilmassasaurus brevicollis

by S. Krasovskiy atrox1.deviantart.com

Conclusion

The description and identification of six isolated quadrates, among which two most probably come from the Kem Kem beds of Morocco, provide additional information on the Cenomanian dinosaur fauna of North Africa. Based on cladistic, geometric morphometric, and phylogenetic morphometric analyses, two morphotypes have been successfully identified as belonging to two species of Spinosaurinae, and ascribed to Spinosaurus aegyptiacus and ?Sigilmassasaurus brevicollis. This study provides the first convincing evidence of two spinosaurine taxa in the Cenomanian of North Africa based on cranial material, casting doubt on the recent reconstruction of a quadrupedal Spinosaurus which may be based on individuals belonging to two different species of Spinosaurinae.

Ontogenetic changes occurring in the spinosaurid quadrates include the suture of the quadrate and quadratojugal, delimitation of the mandibular condyles and squamosal capitulum, and development of a ventral projection of the dorsal quadratojugal contact and a second quadrate ridge ventral to the quadrate head. Based on the quadrate proportions and estimated skull length of Baryonyx and Spinosaurus, quadrates of mature individuals from Morocco belong to animals with a skull length of no more than 120 cm. This suggests that very large forms of Spinosaurus may have been rare in the Kem Kem assemblages.

Morphofunctional analysis of the spinosaurid quadrates has revealed peculiar jaw mechanics in these specialized theropods. An helicoidal and strongly lateromedially oriented joint of the jaw articulation allowed the lateral displacement of the mandibular ramus when the lower jaw was depressed. This lateral movement of the ramus was possible due to a movable mandibular symphysis as the dentaries were joined by connective tissues, and allowed the pharynx to be widened. A similar jaw articulation was convergently present in pterosaurs and particularly pelecanids which also have a mandibular symphysis restricted to the anterior extremity of the mandible. Spinosauridae, which are considered to be semi-aquatic and partially piscivorous animals, were able to swallow large prey such as fish in the same way as pelecanids.

  

Fig 15. Jaw mechanics in the spinosaurid Spinosaurus.
A–D, Mandibular articulation; and F, G, skull in A, C, F–G, lateral; and B, D, anterior views; when A–B, F, the mouth is closed; and C–D, G, fully open, illustrating the lateral movement (in red) of the mandibular ramus for a 45° rotation of the lower jaw (courtesy of Jaime A. Headden); E, skeletal reconstruction of Spinosaurus aegyptiacus by Ibrahim et al. [22]) in swimming position in lateral view with a human (1.8 m) as a scale (modified from Ibrahim et al. [22]). This model is based on spinosaurid cranial and postcranial remains (colored in red) from the Albian-Cenomanian of Northern Africa which possibly belong to two spinosaurine taxa (see also Evers et al. [27]); H, reconstruction of a semi-aquatic Spinosaurus in fishing position (i.e., jaws wide open) in anterolateral view (courtesy of Jason Poole).

Abbreviations: an, angular; ar, articular; d, dentary; ecc, ectocondyle; enc, entocondyle; j, jugal; m, maxilla; n, nasal; p, parietal; pm, premaxilla; po, postorbital; pt, pterygoid; ptf, pterygoid flange; q, quadrate; qf, quadrate foramen; qj, quadratojugal; retp, retroarticular process of the articular; sa, surangular; sq, squamosal.
DOI: 10.1371/journal.pone.0144695

Christophe Hendrickx , Octávio Mateus and Eric Buffetaut. 2016. Morphofunctional Analysis of the Quadrate of Spinosauridae (Dinosauria: Theropoda) and the Presence of Spinosaurus and a Second Spinosaurine Taxon in the Cenomanian of North Africa.
 PLoS ONE. 11(1): e0144695.  DOI: 10.1371/journal.pone.0144695

[Paleontology • 2015] Chilesaurus diegosuarezi • An Enigmatic Plant-eating Theropod from the Late Jurassic period of Chile

Chilesaurus diegosuarezi 
Novas, Salgado, Suárez, Agnolín, Ezcurra, Chimento, de la Cruz, Isasi, Vargas & Rubilar-Rogers, 2015

 DOI: 10.1038/nature14307

Figure 1: Skeletal anatomy of Chilesaurus diegosuarezi gen. et sp. nov.

doi: 10.1038/nature14307

Theropod dinosaurs were the dominant predators in most Mesozoic era terrestrial ecosystems. Early theropod evolution is currently interpreted as the diversification of various carnivorous and cursorial taxa, whereas the acquisition of herbivorism, together with the secondary loss of cursorial adaptations, occurred much later among advanced coelurosaurian theropods. A new, bizarre herbivorous basal tetanuran from the Upper Jurassic of Chile challenges this conception. The new dinosaur was discovered at Aysén, a fossil locality in the Upper Jurassic Toqui Formation of southern Chile (General Carrera Lake). The site yielded abundant and exquisitely preserved three-dimensional skeletons of small archosaurs. Several articulated individuals of Chilesaurus at different ontogenetic stages have been collected, as well as less abundant basal crocodyliforms, and fragmentary remains of sauropod dinosaurs (diplodocids and titanosaurians).

Dental fossils show that Chilesaurus diegosuarezi did not have sharp, bladed teeth as its relative T. rex did. Here is a side view of its right jaw and teeth.

 (Photo: Fernando Novas)

Theropoda Marsh, 1881

Tetanurae Gauthier, 1986

Chilesaurus diegosuarezi gen. et sp. nov.

Etymology. In reference to Chile, and honoring Diego Suárez, who at the age of 7, discovered the first bone remains in the Toqui Formation.

Locality and horizon. Central Patagonian Cordillera, Aysén (Chile; approximately 46° S); Toqui Formation, Tithonian, latest Jurassic.

Chilesaurus diegosuarezihas characteristics of three different dinosaur groups. Its pubic bone points backward like that of an ornithischian dinosaur, perhaps because it provided the gut more surface area with which to digest plant matter, the researchers said. In most carnivorous dinosaurs, the pubic bone points downward or slightly forward, Carr said.

(Image: Gabriel Lío)

Excavating a Chilesaurus skeleton in beds of the Toqui Formation, Southern Andes, Chile.
At first glance, C. diegosuarezi looks like a perplexing mix of different dinosaurs. But "I think what we're really seeing are the expression of limited options that dinosaurs have when they're herbivores," Carr said. "When you take a meat-eating body and you evolve it into an herbivore, there's only so many options that are available."

(photo: Fernando Novas)

Fernando E. Novas, Leonardo Salgado, Manuel Suárez, Federico L. Agnolín, Martín D. Ezcurra, Nicolás R. Chimento, Rita de la Cruz, Marcelo P. Isasi, Alexander O. Vargas and David Rubilar-Rogers. 2015. An Enigmatic Plant-eating Theropod from the Late Jurassic period of Chile. Nature. (2015) DOI: 10.1038/nature14307

 Chilesaurus, a new raptor-like dinosaur with a vegetarian diet. http://po.st/662q2D @SmithsonianMag  

'Bizarre' Jurassic dinosaur discovered in remarkable new find http://gu.com/p/47q7h/stw

7-Year-Old Boy Discovers dinosaur  https://shar.es/1pd7Bn  @LiveScience