Topic
Aucasaurus
About: Aucasaurus is a research topic. Over the lifetime, 11 publications have been published within this topic receiving 277 citations.
Papers
TL;DR: A nearly complete and articulatedskeleton of a large theropod from Auca Mahuevo, a PatagonianLate Cretaceous site famous for its abundant sauropod eggs andembryos, forms the basis for a new abelisaur species, Aucasaurus garridoi.
Abstract: Infoquest Foundation, 160 Cabrini Boulevard #48, New York, New York 10033, U.S.AINTRODUCTIONAbelisaur dinosaurs, theropods with unusual horned skullssuch as Majungatholus (Sampson et al., 1998) and Carnotaurus(Bonaparte, 1985), are the most abundant land predators fromthe Late Cretaceous of Gondwana (Bonaparte, 1996; Novas,1997; Sampson et al., 1998; Coria and Salgado, 1998). Al-though a number of abelisaur species are known from Argentina(Bonaparte, 1996), as well as India and Madagascar (Sampsonet al., 1998), much of their anatomy and evolutionary relation-ships remains poorly understood.In March of 1999, a joint expedition from the Museo Mu-nicipal Carmen Funes and the Natural History Museum of LosAngeles County recovered a nearly complete and articulatedskeleton of a large theropod from Auca Mahuevo, a PatagonianLate Cretaceous site famous for its abundant sauropod eggs andembryos (Chiappe et al., 1998, 2000). In spite of being 30%smaller, the Auca Mahuevo theropod is remarkably similar toCarnotaurus sastrei (Bonaparte, 1985). Nonetheless, a uniquecombination of characters distinguishes the new skeleton fromCarnotaurus sastrei. Thus, following the predicates of the phy-logenetic species concept (Nixon and Wheeler, 1992), the AucaMahuevo skeleton forms the basis for a new abelisaur species,Aucasaurus garridoi.GEOLOGICAL SETTINGThe 150 m-thick section at Auca Mahuevo containing Au-casaurus garridoi runs transitionally from the Anacleto Mem-ber of the Ri´o Colorado Formation up through the Allen For-mation (Fig. 1A). The lower 85 m of the section that comprisesthe Anacleto portion is composed predominantly of pale reddishbrown, fine-grained sandstone, siltstone and mudstone, punc-tuated with occasional beds of greenish gray to light bluishgray, micaceous sandstone. These units appear to represent flu-vial channels and adjacent overbank deposits laid down acrossa low-gradient floodplain (Chiappe et al., 1998; Dingus et al.,2000). The lowest 45 m contain four levels of mudstone andsiltstone that produce fossilized eggs, embryos and embryonicskin of neosauropods (Chiappe et al., 2000). The lowest 20 moccur in a reversed magnetozone tentatively correlated withC33r in the early to middle Campanian portion of the Geomag-netic Polarity Timescale (Dingus et al., 2000). The new speci-men described here was found in an unusual laminated unit,composed by varves of unknown periodicity of greenish graymudstone and very fine-grained sandstone about 70 m abovethe base of the section near the top of the exposures of theAnacleto Member. This bed appears to represent a shallow wa-ter, lacustrine deposit based on the well-developed laminae andthe presence of freshwater arthropods.Institutional Abbreviations MCF-PVPH, Museo Munic-ipal Carmen Funes, Paleontologi´a de Vertebrados, Plaza Huin-cul, Argentina; MACN-CH, Museo Argentino de Ciencias Na-turales, Coleccio´n Chubut, Buenos Aires, Argentina.SYSTEMATIC PALEONTOLOGYTHEROPODA Marsh, 1881ABELISAURIA Novas, 1992ABELISAUROIDEA Novas, 1989ABELISAURIDAE Bonaparte and Novas, 1985CARNOTAURINAE Sereno, 1998CARNOTAURINI new taxonPhylogenetic Definition Carnotaurini is phylogeneticallydefined as the common ancestor of Carnotaurus sastrei andAucasaurus garridoi plus all the descendants of this ancestor.Diagnosis Two unambiguous synapomorphies support themonophyly of carnotaurs (term used to refer to members of theCarnotaurini): the presence of hyposphene–hypantrum articu-lations in the proximal and middle sections of the caudal series,and cranial processes in the epipophyses of the cervical verte-brae. Several other synapomorphies provide further support forthe monophyly of carnotaurs. These, however, are ambiguouslyoptimized because they are not preserved in other abelisaurs.These ambiguous synapomorphies include: a very broad cora-coid (coracoid maximum width three times the distance acrossthe scapular glenoid area), a humerus with a large and hemi-spherical head, an extremely short ulna and radius (ulna to hu-merus ratio 1:3 or less), and frontal prominences (swells orhorns) that are located laterally on the skull roof.Aucasaurus garridoi new taxonEtymology ‘‘Auca,’’ from Mapuche language, in referenceto Auca Mahuevo, the fossil locality where the specimen wasfound; ‘‘saurus,’’ from the Greek, lizard; ‘‘garridoi,’’ in hom-age to Mr. Alberto Garrido, who discovered the holotype.Holotype MCF-PVPH-236 was found lying on its rightside and articulated from the skull to the middle section of thetail (13
149 citations
TL;DR: A new description of the morphology of Pycnonemosaurus nevesi is presented, including three new caudal transverse processes and a discussion of several new characteristics based on perspectives derived from recently described abelisauroids.
Abstract: Abelisaurid theropods were most abundant in the Gondwana during the Cretaceous Period. Pycnonemosaurus nevesi Kellner & Campos, 2002 was the first abelisaurid dinosaur described from the Bauru Group (Brazil, Upper Cretaceous). Nevertheless, its initial description was based on the comparison of a restricted number of remains with other abelisaurids. In this paper, I present a new description of the morphology of Pycnonemosaurus nevesi, including three new caudal transverse processes and a discussion of several new characteristics based on perspectives derived from recently described abelisauroids. Pycnonemosaurus nevesi differs from other abelisaurids based on the following features: a pubis with a small rounded foot and a ventrally-bowed anterior distal end; posterior caudal vertebrae with a hook-shaped transverse process that has an anterodistal expansion that is short and bowed; a strong and massive tibia with a well-developed lateral malleolus that is ventrally expanded. The unfused sutures represent signs of skeletal immaturity, but the specific ontogenetic stage is still uncertain. The current phylogenetic analysis suggests strongly relationship within Pycnonemosaurus and the most-derived abelisaurids (e.g Carnotaurus and Aucasaurus).
97 citations
TL;DR: Examination of these vertebral traits in evolutionary context reveals a progressive sequence of increasing caudofemoral mass and tail rigidity among the Abelisauridae of South America.
Abstract: In the South American abelisaurids Carnotaurus sastrei, Aucasaurus garridoi, and, to a lesser extent Skorpiovenator bustingorryi, the anterior caudal ribs project at a high dorsolateral inclination and have interlocking lateral tips This unique morphology facilitated the expansion of the caudal hypaxial musculature at the expense of the epaxial musculature Distinct ridges on the ventrolateral surfaces of the caudal ribs of Aucasaurus garridoi are interpreted as attachment scars from the intra caudofemoralis/ilio-ischiocaudalis septa, and confirm that the M caudofemoralis of advanced South American abelisaurids originated from a portion of the caudal ribs Digital muscle models indicate that, relative to its overall body size, Carnotaurus sastrei had a substantially larger M caudofemoralis than any other theropod yet studied In most non-avian theropods, as in many extant sauropsids, the M caudofemoralis served as the primary femoral retractor muscle during the locomotive power stroke This large investment in the M caudofemoralis suggests that Carnotaurus sastrei had the potential for great cursorial abilities, particularly short-burst sprinting However, the tightly interlocking morphology of the anterior caudal vertebrae implies a reduced ability to make tight turns Examination of these vertebral traits in evolutionary context reveals a progressive sequence of increasing caudofemoral mass and tail rigidity among the Abelisauridae of South America
63 citations
TL;DR: Despite being fragmentary, MPCN-PV 69 probably represents a new abelisaurid from the Anacleto Formation, thus increasing the knowledge and diversity of Late Cretaceous South American abelISaurids.
29 citations
TL;DR: The abelisaurid braincases described herein show strong consistency in their general morphology and struc- ture, however, there is some variation, and these detailed descriptions are important for understanding the variation and distribution of braincase characters within Abelisauri.
Abstract: The braincases of the abelisaurid theropod dinosaurs Abelisaurus comahuensis and Aucasaurus garridoi are described and compared. These two taxa share the presence of a floccular recess that is '8'-shaped, the absence of a medullar eminence in the floor of the endo- cranial cavity and the possession of a well-developed, nar- row and tall dorsal longitudinal sinus. The basisphenoidal recess is continuous dorsocaudally with two pneumatic cavities, which are separated medially by a thin septum. A connection between the metotic canal and the columel- lar recess that probably represents the exit of cranial nerve IX is observed in Abelisaurus. Aucasaurus has a skull roof with a wide sagittal crest and a low parietal eminence that differentiates it from other derived abeli- saurids such as Abelisaurus, Carnotaurus and Majungasau- rus. The abelisaurid braincases described herein show strong consistency in their general morphology and struc- ture. However, there is some variation, and these detailed descriptions are important for understanding the variation and distribution of braincase characters within Abelisauri- dae.
26 citations
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