[D] Bonapartenykus ultimus ~/~
Describer
Agnolin, Powell, Novas, & Kundrát, 2011
Time
Cretaceous Late Campanian Maastrichtian
Classification
Saurischia Theropoda Tetanurae Coelurosauria Maniraptora Avialae Alvarezsauridae Nomen Nudem
Diet
Carnivore
Fossilsite
Allen Formation, Salitral Ojo de Agua, Rio Negro Province, Argentina
Length
1,5 meter
Info
Abstract
The Alvarezsauridae represents a branch of peculiar basal coelurosaurs with an increasing representation of their Cretaceous radiation distributed worldwide. Here we describe a new member of the group, Bonapartenykus ultimus gen. et sp. nov. from Campanian–Maastrichtian strata of Northern Patagonia, Argentina. Bonapartenykus is represented by a single, incomplete postcranial skeleton.
The morphology of the known skeletal elements suggests close affinities with the previously described taxon from Patagonia, Patagonykus, and both conform to a new clade, here termed Patagonykinae nov. Two incomplete eggs have been discovered in association with the skeletal remains of Bonapartenykus, and several clusters of broken eggshells of the same identity were also found in a close proximity. These belong to the new ooparataxon Arraigadoolithus patagoniensis of the new oofamily Arraigadoolithidae, which provides first insights into unique shell microstructure and fungal contamination of eggs laid by alvarezsaurid theropods.
The detailed study of the eggs sheds new light on the phylogenetic position of alvarezsaurids within the Theropoda, and the evolution of eggs among Coelurosauria. We suggest that plesiomorphic alvarezsaurids survived in Patagonia until the latest Cretaceous, whereas these basal forms became extinct elsewhere.
The new clade Patagonykinae is established in order to include Patagonykus and the new genus Bonapartenykus- The alvarezsaurid-type eggs is unique and constitutes the ootaxon Arraigadoolithidae- Fossil eggshells indicate the presence of fungal contamination- Basal alvarezsaurids persisted in South America until Latest Cretaceous times.
Holotype
MPCA, 1290 (Museo Provincial “Carlos Ameghino”, provincia de Río Negro, Patagonia, Argentina), a nearly articulated but badly preserved partial skeleton consisting of an incomplete mid-dorsal vertebra, a nearly complete left scapulocoracoid, incomplete right scapulocoracoid, incomplete left tibia and femur, nearly complete left pubis articulated with the incomplete pubic peduncle of ilium, and the anterior blade of the left ilium. The specimen was associated with two partially preserved eggs that were separated from this individual by
less than 20 cm
Etymology
The generic name derives from the surname of the great Argentinean palaeontologist José F. Bonaparte and the Latin word onykus (claw). The specific name derives from the Latin word ultimus (latest), because the present record constitutes the geologically youngest alvarezsaurid from South America
Locality and horizon
Salitral Ojo de Agua, Río Negro Province, north-western Patagonia, Argentina. This specimen was found in fluvial sandstones belonging to the Upper levels of the Allen Formation (Campanian–Maastrichtian; Upper Cretaceous; Martinelli and Forasiepi, 2004). This locality has yielded a large variety of non-avian dinosaurs, including remains of ornithischian hadrosaurids, ankylosaurs, and several titanosaurid sauropods; theropods are represented by several incomplete remains of abelisaurids, indeterminate tetanurans, and probable coelurosaurian taxa (Powell, 1987; Coria and Salgado, 2001, 2005; Coria, 2001). In addition, recent findings include an incomplete large alvarezsaurid (Salgado et al., 2009) and the gigantic unenlagiid theropod Austroraptor cabazzai (Novas et al., 2009).
Diagnosis
Largest known alvarezsaurids, diagnosable on the basis of the following unambiguous synapomorphies, not recorded in any other dinosaur: presence of a longitudinal ridge on the lateral surface of coracoid, and strongly sculptured ventral half of coracoid. In addition, both Bonapartenykus and Patagonykus share a medially deflected coracoid, a condition unknown in other alvarezsaurs, but currently widespread among Paraves (Makovicky et al., 2005; ch).
Alvarezsaurid theropod diagnosable on the basis of the following autapomorphies: mid-dorsal vertebrae with spinopostzygapophyseal laminae ending abruptly above the postzygapophyses; ventral portion of coracoid strongly medially deflected and decorated with delicate but profuse grooves (convergently acquired with Xixianykus); fused
scapulocoracoids (convergently acquired with Ceratonykus); scapula with a very wide notch on the posterior margin of the bone; and ilium and pubis fused.
Included taxa
Patagonykus puertai Novas, 1996; Bonapartenykus ultimus gen. et sp. nov. Agnolin, Powell, Novas and Kundrát.Temporal range. Santonian–Maastrichtian (Upper Cretaceous).
Geographic distribution
Neuquén and Río Negro provinces, north-west Patagonia, Argentina
Referred specimens
MGPIFD-GR 166 and MGPIFD-GR 184; both appear to belong to the same individual, consisting of a fragmentary blade of left scapula, an incomplete left coracoid and distal right pubis, and four cervical and a single caudal vertebra described in detail by Salgado et al. (2009).
Although Salgado et al. (2009) described the specimen as belonging to a proximal portion of the pubis, the element may belong to the distal end of the bone. In fact, as occurs in the distal pubis of the holotype of Bonapartenykus, in MGPIFD-GR 166 the preserved portion of the pubis shows a well-developed internal ridge that represents the reduced pubic apron characteristic of the new genus.
The scapula may be referred to Bonapartenykus ultimus on the basis of a very wide and deep notch on the caudal margin of the scapular blade, and the coracoid in which the ventral portion is strongly deflected medially and decorated with delicate but profuse grooves (see Diagnosis). MGPIFD-GR 177, consists of a highly distorted right femur originally described as belonging to Iguanodontia (Coria et al., 2007).
The specimen differs from ornithopods in lacking a pendant fourth trochanter and a basitrochanteric fossa, suggesting its exclusion from Iguanodontia or Ornithopoda (Coria and Salgado, 1996). The specimen is reminiscent of the femur of Patagonykus in having a relatively well-developed and ridge-like fourth trochanter and associated muscle scar. Regrettably, most the shaft of the femur in the holotype of Bonapartenykus is highly distorted; thus, the morphology of the fourth trochanter is unknown.
However, MGPIFD-GR 177 further resembles Bonapatenykus in having a very large and rugous proximal bulge for the m. iliofemoralis externus. In this way, it is probable that the specimens described by Salgado et al. (2009) may, in fact, belong to Bonapartenykus, and that they may pertain to a single individual, on the basis of similar size and preservation.
Included ootaxa
Arraigadoolithus patagoniensis oosp. nov., Kundrát, Novas, Agnolin and Powell; Triprismatoolithus stephensi Jackson and Varricchio, 2010
Agnolin, Powell, Novas, & Kundrát, 2011
Time
Cretaceous Late Campanian Maastrichtian
Classification
Saurischia Theropoda Tetanurae Coelurosauria Maniraptora Avialae Alvarezsauridae Nomen Nudem
Diet
Carnivore
Fossilsite
Allen Formation, Salitral Ojo de Agua, Rio Negro Province, Argentina
Length
1,5 meter
Info
Abstract
The Alvarezsauridae represents a branch of peculiar basal coelurosaurs with an increasing representation of their Cretaceous radiation distributed worldwide. Here we describe a new member of the group, Bonapartenykus ultimus gen. et sp. nov. from Campanian–Maastrichtian strata of Northern Patagonia, Argentina. Bonapartenykus is represented by a single, incomplete postcranial skeleton.
The morphology of the known skeletal elements suggests close affinities with the previously described taxon from Patagonia, Patagonykus, and both conform to a new clade, here termed Patagonykinae nov. Two incomplete eggs have been discovered in association with the skeletal remains of Bonapartenykus, and several clusters of broken eggshells of the same identity were also found in a close proximity. These belong to the new ooparataxon Arraigadoolithus patagoniensis of the new oofamily Arraigadoolithidae, which provides first insights into unique shell microstructure and fungal contamination of eggs laid by alvarezsaurid theropods.
The detailed study of the eggs sheds new light on the phylogenetic position of alvarezsaurids within the Theropoda, and the evolution of eggs among Coelurosauria. We suggest that plesiomorphic alvarezsaurids survived in Patagonia until the latest Cretaceous, whereas these basal forms became extinct elsewhere.
The new clade Patagonykinae is established in order to include Patagonykus and the new genus Bonapartenykus- The alvarezsaurid-type eggs is unique and constitutes the ootaxon Arraigadoolithidae- Fossil eggshells indicate the presence of fungal contamination- Basal alvarezsaurids persisted in South America until Latest Cretaceous times.
Holotype
MPCA, 1290 (Museo Provincial “Carlos Ameghino”, provincia de Río Negro, Patagonia, Argentina), a nearly articulated but badly preserved partial skeleton consisting of an incomplete mid-dorsal vertebra, a nearly complete left scapulocoracoid, incomplete right scapulocoracoid, incomplete left tibia and femur, nearly complete left pubis articulated with the incomplete pubic peduncle of ilium, and the anterior blade of the left ilium. The specimen was associated with two partially preserved eggs that were separated from this individual by
less than 20 cm
Etymology
The generic name derives from the surname of the great Argentinean palaeontologist José F. Bonaparte and the Latin word onykus (claw). The specific name derives from the Latin word ultimus (latest), because the present record constitutes the geologically youngest alvarezsaurid from South America
Locality and horizon
Salitral Ojo de Agua, Río Negro Province, north-western Patagonia, Argentina. This specimen was found in fluvial sandstones belonging to the Upper levels of the Allen Formation (Campanian–Maastrichtian; Upper Cretaceous; Martinelli and Forasiepi, 2004). This locality has yielded a large variety of non-avian dinosaurs, including remains of ornithischian hadrosaurids, ankylosaurs, and several titanosaurid sauropods; theropods are represented by several incomplete remains of abelisaurids, indeterminate tetanurans, and probable coelurosaurian taxa (Powell, 1987; Coria and Salgado, 2001, 2005; Coria, 2001). In addition, recent findings include an incomplete large alvarezsaurid (Salgado et al., 2009) and the gigantic unenlagiid theropod Austroraptor cabazzai (Novas et al., 2009).
Diagnosis
Largest known alvarezsaurids, diagnosable on the basis of the following unambiguous synapomorphies, not recorded in any other dinosaur: presence of a longitudinal ridge on the lateral surface of coracoid, and strongly sculptured ventral half of coracoid. In addition, both Bonapartenykus and Patagonykus share a medially deflected coracoid, a condition unknown in other alvarezsaurs, but currently widespread among Paraves (Makovicky et al., 2005; ch).
Alvarezsaurid theropod diagnosable on the basis of the following autapomorphies: mid-dorsal vertebrae with spinopostzygapophyseal laminae ending abruptly above the postzygapophyses; ventral portion of coracoid strongly medially deflected and decorated with delicate but profuse grooves (convergently acquired with Xixianykus); fused
scapulocoracoids (convergently acquired with Ceratonykus); scapula with a very wide notch on the posterior margin of the bone; and ilium and pubis fused.
Included taxa
Patagonykus puertai Novas, 1996; Bonapartenykus ultimus gen. et sp. nov. Agnolin, Powell, Novas and Kundrát.Temporal range. Santonian–Maastrichtian (Upper Cretaceous).
Geographic distribution
Neuquén and Río Negro provinces, north-west Patagonia, Argentina
Referred specimens
MGPIFD-GR 166 and MGPIFD-GR 184; both appear to belong to the same individual, consisting of a fragmentary blade of left scapula, an incomplete left coracoid and distal right pubis, and four cervical and a single caudal vertebra described in detail by Salgado et al. (2009).
Although Salgado et al. (2009) described the specimen as belonging to a proximal portion of the pubis, the element may belong to the distal end of the bone. In fact, as occurs in the distal pubis of the holotype of Bonapartenykus, in MGPIFD-GR 166 the preserved portion of the pubis shows a well-developed internal ridge that represents the reduced pubic apron characteristic of the new genus.
The scapula may be referred to Bonapartenykus ultimus on the basis of a very wide and deep notch on the caudal margin of the scapular blade, and the coracoid in which the ventral portion is strongly deflected medially and decorated with delicate but profuse grooves (see Diagnosis). MGPIFD-GR 177, consists of a highly distorted right femur originally described as belonging to Iguanodontia (Coria et al., 2007).
The specimen differs from ornithopods in lacking a pendant fourth trochanter and a basitrochanteric fossa, suggesting its exclusion from Iguanodontia or Ornithopoda (Coria and Salgado, 1996). The specimen is reminiscent of the femur of Patagonykus in having a relatively well-developed and ridge-like fourth trochanter and associated muscle scar. Regrettably, most the shaft of the femur in the holotype of Bonapartenykus is highly distorted; thus, the morphology of the fourth trochanter is unknown.
However, MGPIFD-GR 177 further resembles Bonapatenykus in having a very large and rugous proximal bulge for the m. iliofemoralis externus. In this way, it is probable that the specimens described by Salgado et al. (2009) may, in fact, belong to Bonapartenykus, and that they may pertain to a single individual, on the basis of similar size and preservation.
Included ootaxa
Arraigadoolithus patagoniensis oosp. nov., Kundrát, Novas, Agnolin and Powell; Triprismatoolithus stephensi Jackson and Varricchio, 2010