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A unique multitoothed ornithomimosaur dinosaur from the Lower Cretaceous of Spain
Abstract
THE Lower Cretaceous lithographic limestones from Las Hoyas (province of Cuenca, Spain) have yielded important vertebrate fossil remains. We report here a new specimen, the first ornithomimosaur theropod found in Europe. Pelecanimimus polyodon gen. et sp. nov., has some striking elements preserved, such as the hyoid, sternum and integumentary impressions. The fossil has revealed other unexpected features, including a derived hand in an ancient ornithomimosaur, and a large number of teeth (over 200) with a distinctive morphology. This specimen suggests an alternative evolutionary process towards the toothless condition in Ornithomi-mosauria, which could be explained by an exaptation. Pelecanimimus polyodon stresses the relationship between Troodontidae and Ornithomimosauria.
Supplementary resources (3)
... Hitchcock, 1841;Gatesy, 2001;Currie, Badamgarav & Koppelhus, 2003;Milner, Lockley & Johnson, 2006a;Milner, Lockley & Kirkland, 2006b;Kim et al., 2019). Smooth or bare skin has been noted in the contentious tetanuran Sciurumimus (Rauhut et al., 2012) and the ornithomimosaurian Pelecanimimus (Pérez- Moreno et al., 1994;Briggs et al., 1997), whereas the remarkably preserved skin (epidermis) and other soft tissues have been described in the tyrannosauroid Santanaraptor (Kellner, 1996;Kellner & de Campos, 1998). Scansoriopterygids, bizarre early-diverging pennaraptorans that evolved a unique airfoil formed from a membranous patagium Wang et al., 2019), illustrate the extent to which epidermal structures played a role in forming disparate morphologies and ecologies among theropods. ...
... Within 6 years, several major discoveries were announced that revolutionised our understanding of the morphological diversity of theropod integument and the evolution of feathers. Pérez-Moreno et al. (1994) and Kellner (1996) reported soft tissue and integumentary structures in the early-diverging ornithomimosaurian Pelecanimimus polyodon and the tyrannosauroid Santanaraptor placidus from the Early Cretaceous of Spain and Brazil, respectively. In 1997, skin morphology was revealed in tyrannosaurid theropods, with a specimen of Gorgosaurus libratus being described as having small rounded or hexagonal scales on the tail (Carpenter, 1997). ...
... Whereas the vast majority of Maniraptoriformes lost an extensive squamous body covering in 'exchange' for feathers (Campione, Barrett & Evans, 2020;Bell & Hendrickx, 2021), at least two ornithomimosaurians, Pelecanimimus polyodon and Ornithomimus sp., are reported to have had smooth, scaleless skin on parts of their bodies (Briggs et al., 1997;van der Reest, Wolfe & Currie, 2016), although the latter was largely covered in feathers (Zelenitsky et al., 2012;van der Reest, Wolfe & Currie, 2016). Pérez-Moreno et al. (1994) originally described the soft tissue structures associated with the holotype of Pelecanimimus; however, these were later prepared off to expose the skeleton. Therefore, most evidence of the soft tissues is now missing and only a few low-resolution photographs remain (Fig. 14A, B). ...
Modern birds are typified by the presence of feathers, complex evolutionary innovations that were already widespread in the group of theropod dinosaurs (Maniraptoriformes) that include crown Aves. Squamous or scaly reptilian-like skin is, however, considered the plesiomorphic condition for theropods and dinosaurs more broadly. Here, we review the morphology and distribution of non-feathered integumentary structures in non-avialan theropods, covering squamous skin and naked skin as well as dermal ossifications. The integumentary record of non-averostran theropods is limited to tracks, which ubiquitously show a covering of tiny reticulate scales on the plantar surface of the pes. This is consistent also with younger averostran body fossils, which confirm an arthral arrangement of the digital pads. Among averostrans, squamous skin is confirmed in Ceratosauria (Carnotaurus), Allosauroidea (Allosaurus, Concavenator, Lourinhanosaurus), Compsognathidae (Juravenator), and Tyrannosauroidea (Santanaraptor, Albertosaurus, Daspletosaurus, Gorgosaurus, Tarbosaurus, Tyrannosaurus), whereas dermal ossifications consisting of sagittate and mosaic osteoderms are restricted to Ceratosaurus. Naked, non-scale bearing skin is found in the contentious tetanuran Sciurumimus, possibly ornithomimosaurians (Pelecanimimus) and tyrannosauroids (Santanaraptor), and also on the patagia of scansoriopterygids (Ambopteryx, Yi). Scales are surprisingly conservative among non-avialan theropods compared to some dinosaurian groups (e.g. hadrosaurids); however, the limited preservation of tegument on most specimens hinders further interrogation. Scale patterns vary among and/or within body regions in Carnotaurus, Concavenator and Juravenator, and include polarised, snake-like ventral scales on the tail of the latter two genera. Unusual but more uniformly distributed patterning also occurs in Tyrannosaurus, whereas feature scales are present only in Albertosaurus and Carnotaurus. Few theropods currently show compelling evidence for the co-occurrence of scales and feathers (e.g. Juravenator, Sinornithosaurus), although reticulate scales were probably retained on the mani and pedes of many theropods with a heavy plumage. Feathers and filamentous structures appear to have replaced widespread scaly integuments in maniraptorans. Theropod skin, and that of dinosaurs more broadly, remains a virtually untapped area of study and the appropriation of commonly used techniques in other palaeontological fields to the study of skin holds great promise for future insights into the biology, taphonomy and relationships of these extinct animals.
... The parasphenoids form an anteroposteriorly-elongated cultriform process (parasphenoid rostrum) with deep ventral concavity continuous with the fossa present anteriorly on the basisphenoids (Fig. 12F). Laterally, the base of the cultriform process is slightly pneumatized by a shallow fossa (Fig. 12C, E) and lacks apparent parasphenoid bulla unlike those of highly pneumatized taxa such as late-diverging troodontids (Barsbold, 1974;Currie, 1985) and ornithomimosaurs (Osmólska et al., 1972;Barsbold, 1981;Pérez-Moreno et al., 1994;Kobayashi and Lü, 2003;Tahara and Larsson, 2011). ...
... Metacarpal I is considerably shorter than other metacarpals unlike those of ornithomimids (Pérez-Moreno et al., 1994), with its length about the half of metacarpal II and 60% of metacarpal III, while its length being greater than the width ( Table 7). The element is dorsoventrally thin and mediolaterally wide in contrast to metacarpal III (Fig. 48Y). ...
A bizarre coelurosaurian theropod Fukuivenator paradoxus is known only from the holotype specimen preserving majority of the skeleton from the Kitadani Dinosaur Quarry of the Lower Cretaceous Kitadani Formation, Tetori Group, Fukui, Japan. With aids of computed tomography techniques, a re-examination of the holotype specimen reveals additional features of Fukuivenator which was unobservable in the original description, such as the presence of parietals and a quadrate, and the fusion of the posteriormost caudal vertebrae. The thorough description in this study results in the emendation of diagnosis including the retraction of the large promaxillary fenestra subequal in size to maxillary fenestra, and the addition of the large maxillary fenestra expanded well dorsally above the suprantral strut. Expansion of morphological information elaborates the phylogenetic dataset, resulting in locating Fukuivenator as an unambiguous member of Maniraptora at the basalmost position of Therizinosauria. This phylogenetic position of Fukuivenator is supported by several therizinosaurian synapomorphies such as the subotic recess on the braincase, 11 cervical vertebrae some of which having two pneumatic foramina, and distal articular condyles on the anterior surface of the humerus. Among numerous diagnostic features, eight characters shared with some non-maniraptoran coelurosaurs and five shared with different clades within Maniraptora, highlighting the notably mosaic condition of Fukuivenator proposed in the original description. The combination of characters for herbivorous and carnivorous diets suggests the omnivory of Fukuivenator, projecting the dietary shift in the earliest evolutionary stage of Therizinosauria. Also, the large olfactory ratio revealed by the revised brain endocast highlights the unusually high olfactory acuity further developed than the plesiomorphic condition, implying that the acute sense of smell might be a characteristic of therizinosaurian theropods.
... Standing among the Secondary consumer vertebrates are predators that possibly fed on invertebrates, such as the terrestrial albanerpetontid lyssamphibian Celtedens, and probably the eutriconodont mammal Spinolestes (Fig. 6and Box 1). Insectivory has also been attributed to the small crocodyliform Cassissuchus(Buscalioni 2017; Fig. 6) and the medium-sized and ornithomimid dinosaur Pelecanimimus, according to its unique dentition (multitoothed rows, with dozens of small teeth)(Pérez-Moreno et al. 1994). The status of Tertiary consumer remains difficult to allocate to any taxa in the land environment because there are no strictly identifiable carnivore tetrapods; the carcharodontosaurid Concavenator(Ortega et al. 2010;Cuesta et al. 2019), the largest animal recorded at Las Hoyas(Fig. ...
Las Hoyas (Cuenca, Spain) represents a unique Lower Cretaceous (Barremian) fossil biota of a wetland. The site has yielded a particularly diverse assemblage of more than twenty thousand plant and animal fossils, many of which present unprecedented soft-tissue preservation, including microstructural details. Among the most significant discoveries are the oldest angiosperms, the smallest species of chondrichtians and squamates, new theropod dinosaurs, including several enantiornithine birds, the first European tapejarid pterosaur and the most complete Eutriconodont mammal. Such discoveries have produced data on important aspects related to plant and animal evolution, such as the first steps in flower development by plants, insight on unknown anatomical and diet specializations in theropod dinosaurs, the development of flight maneuverability in early birds, the unexpected global distribution of tapejarid dinosaurs, and groundbreaking data on early mammalian hair development. There are many more discoveries to unveil and new research is now liking the immense wealth of paleobiological information with mathematical procedures to study the ecological structure of the wetland.
Supplementary material: https://doi.org/10.6084/m9.figshare.c.6336914
... Ornithomimosaurs repeatedly evolved gigantic body size during their evolutionary history [14,69,[112][113][114] (Fig 9), although evidence for directional mass evolution, as opposed to stochastic processes, is lacking [115]. Early-diverging ornithomimosaurs from the Early Cretaceous (pre-Albian), such as Nqwebasaurus thwazi [90] from Africa, Hexing qingyi [101], Shenzhousaurus orientalis [106], and Kinnareemimus khonkaenensis [103,116] from Asia, Pelecanimimus polyodon [104,117] from Europe, and Nedcolbertia justinhofmanni [15,118] from North America) were universally small bodied (>12 kg [115, S1 Table]). During the Albian, ornithomimosaurs generally exhibit a trend of increasing body size, although a mosaic of small, medium, and large bodied species existed (Figs 2 and 9). ...
Reconstructing the evolution, diversity, and paleobiogeography of North America's Late Cretaceous dinosaur assemblages require spatiotemporally contiguous data; however, there remains a spatial and temporal disparity in dinosaur data on the continent. The rarity of vertebrate-bearing sedimentary deposits representing Turonian-Santonian ecosystems, and the relatively sparse record of dinosaurs from the eastern portion of the continent, present persistent challenges for studies of North American dinosaur evolution. Here we describe an assemblage of ornithomimosaurian materials from the Santonian Eutaw Formation of Mississippi. Morphological data coupled with osteohistological growth markers suggest the presence of two taxa of different body sizes, including one of the largest ornithomimosaurians known worldwide. The regression predicts a femoral circumference and a body mass of the Eutaw individuals similar to or greater than that of large-bodied ornithomimosaurs, Beishanlong grandis, and Gallimimus bullatus. The paleoosteohistology of MMNS VP-6332 demonstrates that the individual was at least ten years of age (similar to B. grandis [~375 kg, 13-14 years old at death]). Additional pedal elements share some intriguing features with ornithomimosaurs, yet suggest a larger-body size closer to Deino-cheirus mirificus. The presence of a large-bodied ornithomimosaur in this region during this time is consistent with the relatively recent discoveries of early-diverging, large-bodied ornithomimosaurs from mid-Cretaceous strata of Laurasia (Arkansaurus fridayi and B. grandis). The smaller Eutaw taxon is represented by a tibia preserving seven growth cycles, with osteohistological indicators of decreasing growth, yet belongs to an individual approaching somatic maturity, suggesting the coexistence of medium-and large-bodied ornithomimosaur taxa during the Late Cretaceous Santonian of North America. The Eutaw ornithomimosaur materials provide key information on the diversity and distribution of North American ornithomimosaurs and Appalachian dinosaurs and fit with broader evidence of PLOS ONE PLOS ONE | https://doi.org/10.1371/journal.pone.
... Trackmaker recognition of this abnormal and pathological trackway should be carefully considered. Small-to medium-sized avian and non-avian theropods that characterise the Las Hoyas diversity, such as the enantiornithes [69][70][71], and ornithomimosaur, Pelecanimimus polyodon [72] were discarded as putative producers due to their body size. The carcharodontosaurid, Concavenator corcovatus [73][74] was also discarded because it shows a pes of half the size of the magenta footprints with short and subequal toes. ...
We describe a trackway (LH-Mg-10-16) occurring in laminated carbonated limestones of the Las Hoyas locality, Serranía de Cuenca, Spain. It is unmistakably a large theropod dinosaur trackway encompassing two unusual aspects, namely, wide-steps, and a set of equally deformed left footprints (with a dislocated digit). The layer also preserves other vertebrate trails (fish Undichna ) and different impressions in the sediment. To address these complex settings, we devised a multidisciplinary approach, including the ichnological and taphonomical descriptions, characterisation of the rock lithofacies using thin-sections, 3D structured-light digitalisation with a high precision of 200–400 μm, and a geometric morphometric comparison with a large sample of bipedal dinosaur trackways. Sedimentary analyses showed that the trackway was produced in a humid, benthonic microbial mat, the consistency and plasticity of which enabled the preservation of the details of the movement of the animal. The results of the geometric analysis indicate that the “wide-steps” of the trackway is not unusual compared to other trackways, providing evidence that it was made by a single individual with an estimated hip height approximately 2 m. Analogous pathologies in extant archosaurs that yield the combination of wide steps and deformed digits in the same trackway were considered. All results mutually support the hypothesis that a large theropod dinosaur, with a pathological foot, generated the trackway as it crossed an area of shallow water while slowly walking towards the main water source, thus stepping steadily over the benthonic mat over which multiple fish were swimming.
... Ornithomimosaurs repeatedly evolved gigantic body size during their evolutionary history [14,69,[112][113][114] (Fig 9), although evidence for directional mass evolution, as opposed to stochastic processes, is lacking [115]. Early-diverging ornithomimosaurs from the Early Cretaceous (pre-Albian), such as Nqwebasaurus thwazi [90] from Africa, Hexing qingyi [101], Shenzhousaurus orientalis [106], and Kinnareemimus khonkaenensis [103,116] from Asia, Pelecanimimus polyodon [104,117] from Europe, and Nedcolbertia justinhofmanni [15,118] from North America) were universally small bodied (>12 kg [115, S1 Table]). During the Albian, ornithomimosaurs generally exhibit a trend of increasing body size, although a mosaic of small, medium, and large bodied species existed (Figs 2 and 9). ...
Reconstructing the evolution, diversity, and paleobiogeography of North America’s Late Cretaceous dinosaur assemblages requires spatiotemporally contiguous data; however, there remains a spatial and temporal disparity in dinosaur data on the continent. The rarity of vertebrate-bearing sedimentary deposits representing Turonian–Santonian ecosystems, and the relatively sparse record of dinosaurs from the eastern portion of the continent, present persistent challenges for studies of North American dinosaur evolution. Here we describe an assemblage of ornithomimosaurian materials from the Santonian Eutaw Formation of Mississippi. Morphological data coupled with osteohistological growth markers suggest the presence of two taxa of different body sizes, including one of the largest ornithomimosaurians known worldwide. The regression predicts a femoral circumference and a body mass of the Eutaw individuals similar to or greater than that of large-bodied ornithomimosaurs, Beishanlong grandis and Gallimimus bullatus . The paleohistology of MMNS VP-6332 demonstrates that the individual was at least 11 years of age (similar to B. grandis [~375 kg, 13–14 years old at death]). Additional pedal elements share some intriguing features with ornithomimosaurs yet suggest a larger-body size closer to Deinocheirus mirificus . The presence of a large-bodied ornithomimosaur in this region during this time is consistent with the relatively recent discoveries of early-diverging, large-bodied ornithomimosaurs from mid-Cretaceous strata of Laurasia ( Arkansaurus fridayi and B. grandis ). The smaller Eutaw taxon is represented by a tibia preserving seven growth cycles, with osteohistological indicators of decreasing growth, yet belongs to an individual with near reaching somatic maturity of the larger taxon, suggesting the co-existence of medium- and large-bodied ornithomimosaur taxa during the Late Cretaceous Santonian of North America. The Eutaw ornithomimosaur materials provide key information on the diversity and distribution of North American ornithomimosaurs and Appalachian dinosaurs and fit with broader evidence of multiple cohabiting species of ornithomimosaurian dinosaurs in Late Cretaceous ecosystems of Laurasia.
... Isasmendi et al., 2020;Malafaia et al., 2020aMalafaia et al., , 2020b, carcharodontosaurids (Gasca et al., 2014a;Ortega et al., 2010), and coelurosaurs (e.g. Torrente et al., 2018) such as ornithomimosaurs (Cuesta et al., 2021;Pérez-Moreno et al., 1994). The ornithischian dinosaurs are mainly ankylosaurs (Gasulla et al., 2011;Pereda-Suberbiola et al., 2007) and ornithopods. ...
The El Castellar Formation (upper Hauterivian-lowermost Barremian, Lower Cretaceous) in the southwest of the Maestrat Basin (Spain) has yielded diverse dinosaur remains, mostly fragmentary bones. This study describes, morphometrically analyses, and compares several isolated postcranial fossils of large ornithopods from three new different sites in the municipality of Cabra de Mora (Peñagolosa sub-basin, Teruel Province). The fossils are attributed to styracosternan ornithopods, and some of them are related to the species Iguanodon galvensis, representing the oldest known record related to this taxon in the Iberian Peninsula. Moreover, this study verifies the hypothesis of the coexistence of at least two different styracosternans—a medium-sized form and a large-sized one—during the late Hauterivian-early Barremian in the Peñagolosa sub-basin. In addition, we formally describe the first dinosaur tracksite of the El Castellar Formation in this sub-basin. All ichnites are preserved as natural casts, and their trackmakers are likely to have been related to large styracosternans. Hence, the evidence provided here by both bones and tracks supports the idea that large ornithopods were the predominant dinosaurs in the wetlands of an extensive coastal plain.
This Doctoral Thesis presents an exhaustive review of the Patagonian alvarezsaurids (Dinosauria, Theropoda). It includes a detailed osteological description of specimens of Patagonykus puertai (Holotype, MCF-PVPH-37), cf. Patagonykus puertai (MCF-PVPH-38), Patagonykinae indet. (MCF-PVPH-102), Alvarezsaurus calvoi (Holotype, MUCPv-54), Achillesaurus manazzonei (Holotype, MACN-PV-RN 1116), Bonapartenykus ultimus (Holotype, MPCA 1290), and cf. Bonapartenykus ultimus (MPCN-PV 738). A phylogenetic analysis and a discussion about the taxonomic validity of the recognized species and the taxonomic assignment of the materials MCF-PVPH-38, MCF-PVPH-102 and MPCN-PV 738 are presented. Different evolutionary and paleobiological studies were carried out in order to elucidate functional and behavioral aspects.
Alvarezsaurus calvoi (MUCPv-54), Achillesaurus manazzonei (MACN-PV-RN 1116), Patagonykus puertai (MCF-PVPH-37) and Bonapartenykus ultimus (MPCA 1290) are valid species due to the presence of many autapomorphies. In this sense, the hypothesis proposed by P. Makovicky and collaborators that Achillesaurus manazzonei is a junior synonym of Alvarezsaurus calvoi is rejected. Likewise, certain morphological evidence allows hypothesizing that Alvarezsaurus calvoi represents a growth stage earlier than skeletal maturity. Specimen MCF-PVPH-38 is referable as cf. Patagonykus puertai, while MCF-PVPH-102 is considered an indeterminate Patagonykinae. In turn, MPCN-PV 738 is assigned as cf. Bonapartenykus ultimus based on the little overlapping material with the Bonapartenykus ultimus holotype.
The results obtained from the mineralogical characterization through the X-ray diffraction method of specimens MPCN-PV 738 and the holotype of Bonapartenykus ultimus (MPCA 1290), allow to suggest that both specimens come from the same geographical area and stratigraphic level.
The phylogenetic analysis, which is based upon the matrix of Gianechini and collaborators of 2018 with the inclusion of proper characters, and the database of Xu and collaborators of 2018, recovered the South American members of Alvarezsauria, such as Alnashetri cerropoliciensis (Candeleros Formation; Cenomanian), Patagonykus puertai (Portezuelo Formation, Turonian-Coniacian), Alvarezsaurus calvoi and Achillesaurus manazzonei (Bajo de La Carpa Formation, Coniacian-Santonian), and Bonapartenykus ultimus (Allen Formation, Campanian-Maastrichtian), nesting within the family Alvarezsauridae. In this sense, the forms that come from the Bajo de La Carpa Formation (Coniacian-Santonian) are recovered at the base of the Alvarezsauridae clade, while Alnashetri cerropoliciensis nests as a non-Patagonykinae alvarezsaurid. Regarding the type specimens of Patagonykus puertai and Bonapartenykus ultimus, they are recovered as members of the Patagonykinae subclade, a group that is recovered as a sister taxon of Parvicursorinae, both nested within the Alvarezsauridae. In addition, the topology obtained allows discerning the pattern, rhythm and time of evolution of the highly strange and derived alvarezsaurian skeleton, concluding in a gradual evolution. The Bremer and Bootstrap supports of the nodes (Haplocheirus + Aorun), [Bannykus + (Tugulusaurus + Xiyunykus)], and Patagonykinae, show indices that represent very robust values for these nodes. Likewise, these values suggest that two endemic clades originated early in Asia, while one endemic clade is observed in Patagonia, i.e., Patagonykinae.
The analysis of the directional trends of the Alvarezsauria clade, tested by means of a own database on body masses based on the Christiansen and Fariña method, subsequently calibrated with the group's phylogeny using the R software, shows two independent miniaturization events in the alvarezsaurid evolution, namely the former originating from the base of the Alvarezsauridae (sustained by Alvarezsaurus), and the latter within the Parvicursorinae. Analysis of the Alvarezsauria dentition reveals possible dental synapomorphies for the Alvarezsauria clade that should be tested in an integrative phylogenetic analysis. The general characterization of the forelimb and a partial reconstruction of the myology of alvarezsaurs demonstrate different configurations for Patagonykinae and Parvicursorinae. The multivariate analyzes carried out from the databases of Elissamburu and Vizcaíno, plus that of Cau and collaborators, show that the Patagonykinae would have had ranges of movements greater than those observed in Parvicursorinae, although the latter would have had a greater capacity to carry out more strenuous jobs. The morphometric analysis of the hindlimb and the use of the Snively and collaborators equations, show that the configuration of this element in Alvarezsauria is indicative of a highly cursorial lifestyle, as well as possible particular strategies for more efficient locomotion. The topology obtained in the phylogenetic analysis that was carried out in this Doctoral Thesis, allowed clarifying the ontogenetic changes observed in the ontogenetic series of the manual ungueal element II-2 within the clade Alvarezsauridae. In addition, the multivariate analysis carried out from the manual phalanx II-2 allows us to infer that alvarezsaurs could have performed functions such as hook-and-pull and piercing, where the arm would function as a single unit. The anatomy and myology of the alvarezsaurian tail show that the caudal vertebrae of alvarezsaurians exhibit a combination of derived osteological features that suggests functions unique among theropods, such as considerable dorsal and lateral movements, as well as exceptional abilities to support distal loading of their long tail without compromising stability and/or mobility.
A newly identified ornithomimosaurian pelvis and sacrum from the Upper Cretaceous Erlian Formation of Nei Mongol, China is described in detail in this paper. This specimen is distinguished from previously described taxa by the presence of a combination of features that is unique among Ornithomimosauria: sacrum comprising five vertebrae with neural spines fused into a continuous plate, iliac posterior end rectangular, pubic shaft distally straight, ischial boot not broadened transversely, and ischial shaft proximally straight, distally curved, and 80 percent as long as the pubis. This specimen differs from at least some material assigned to the sympatric Archaeornithomimus asiaticus, showing that two distinct ornithomimosaurian taxa are present in this Late Cretaceous fossiliferous rock unit. A phylogenetic analysis places LH-02-01 in a relatively early-diverging position within Ornithomimosauria, outside the two major clades Deinocheiridae and Ornithomimidae, but its relationships with other early-diverging ornithomimosaurs remain unresolved. The primitive nature of LH-02-01 adds to the evidence from fossil vertebrates that the Erlian Formation correlates with the Turonian Bissekty Formation of Uzebekistan, while the biostratigraphic evidence from non-vertebrates instead indicates a Campanian to Maastrichtian age for the Erlian Formation. This apparent contradiction remains unresolved, pending future research aimed at reconciling the seemingly incompatible lines of evidence.
A total of 227 theropod teeth have so far been recovered from the upper Campanian Laño site (northern Iberian Peninsula). The teeth were studied for their qualitative and quantitative features. From the theropod sample found at Laño, seven morphotypes attributed to five taxa are identified: a medium to large abelisaurid (Arcovenator sp.) and four small coelurosaurians (Dromaeosauridae indet., Paraves indet., cf. Paronychodon sp. and cf. Richardoestesia sp.) Together with the ground bird Gargantuavis and a possible ornithomimosaur, the theropod fauna of Laño might be composed of two medium–large-sized non-avian theropods, four small-bodied non-avian theropods and a large terrestrial bird. This makes the Laño site the richest and most diverse latest Cretaceous theropod site in Europe. Furthermore, the Laño site and the Upper Cretaceous localities of Europe that have yielded theropod remains suggest that the medium–large-sized theropods were abelisaurids or indeterminate theropods. The small theropods are more abundant, diverse and represented by different dromaeosaurids, Paronychodon, Richardoestesia or related forms, troodontids and, probably, by other paravians. Of the birds, enantiornithines, gargantuaviids and ornithurines are also common in the European Upper Cretaceous sites. The theropod assemblage of Laño, together with the taxa of other Upper Cretaceous sites, supports the idea that several theropod dispersal events took place during the Cretaceous. This resulted in a mixture of European endemic, Asiamerican and Gondwanan forms. This study also supports the hypothesis that the intra-Maastrichtian faunal turnover that occurred in the Ibero-Armorican landmass seems to have had no apparent effect on theropods.
The Neocomian Spanish outcrops of Montsec (province of Lérida) and the new one of Las Hoyas (province of Cuenca) have yielded several avian remains in the last few years. Several isolated feathers have been reported from Montsec, and a specimen of some feathered wing bones has recently been found. Las Hoyas has yielded an isolated feather and a nearly articulated small fossil bird that lacks the skull. This new specimen, reported here, presents a combination of derived (strut-like coracoids, pygostyle) and primitive (pelvic girdle, sacrum, hind limb) character states. If one considers Archaeopteryx, Ornithurae and the new Spanish fossil bird, it seems clear that the latter taxon is the sister group of Ornithurae (extant birds and all other fossil birds that are closer to recent forms than is Archaeopteryx).
The family Ornithomimidae is defined on the basis of the skeletal morphology of the three genera Ornithomimus, Struthiomimus, and Dromiceiomimus known in continental strata in Alberta, which are temporally equivalent to the Upper Campanian substage. At least two genera occur in Canadian Lance (Upper Maestrichtian) equivalent strata, but cannot be identified at present. A group of more primitive ornithomimoid theropods is represented else-where by the late Jurassic Elaphrosaurus and early Cretaceous Archaeornithomimus.Ornithomimid attributes include a general body form which parallels that of the ratites; elongate forelimbs, a kinetic skull, enormous eyes, a relatively highly evolved brain, and possibly a secondary palate and supertemporal fenestrae which were nearly encircled by alae of the squamosal. A reconstruction of the myology of the thigh indicates that ornithomimids were extremely fleet, but lacked the agility characteristic of modern large ground birds. They probably subsisted on small, soft-bodi...
An articulated skeleton of a 1 m long theropod from Early Cretaceous strata in Inner Mongolia is clearly referrable to the Troodontidae, representing the most complete specimen known of this group of small carnivorous dinosaurs. The tail and neck of the animal were curled next to its body upon burial; the upper surface of the skeleton was badly damaged by erosion. Previously unknown details of troodont morphology include a quadratic contact with the braincase wall (forming part of a channel leading to the lateral depression), a presacral vertebral count possibly similar to that of most theropods, absence of ossified caudal tendons, presence of a rod-like clavicle, and absence of sternal ossifications. A new genus and species (Sinornithoides youngi n.gen., n. sp.) is established for the specimen on the basis of its short skull, laterally directed orbital rim of the frontal, and elongated hind limb. A reassessment of character distributions in other small theropods and primitive birds must be completed before troodontid affinities can be established with greater precision.
The fossiliferous beds of Las Hoyas (province ofCuenca, Spain) are composed of limestones (probably Late Hauterivian). The main fossiliferous facies consists of laminated limestone from a lake-basin plain with bottom waters perennially anoxic. The floral and faunal assemblage is similar to that of Montsech (prov. of Lérida, Spain), with divergences especially in the insects and some tetrapods. Bottom-dwelling invertebrates are scarce. Most of invertebrates are arthropods: three crustaceans and a relatively diversified entomofauna. The fishes are the main component of the vertebrate fauna both in number of individuals and diversity (13 different taxa). Among tetrapods the most abundant is a new genus of Caudata. Reptiles are represented by a chelonian, a little lizard and an atoposaurid crocodile. Finally, a new bird is reported from Las Hoyas, with an intermediate phylogenetic position between Archaeopteryx and Ornithurae.RésuméLes couches à fossiles de Las Hoyas (province deCuenca, Espagne) sont composées de calcaires d'âge Hauterivien supérieur — Barrémien inférieur, probablement) de milieu lacustre. Le principal faciès fossilifère est fait de calcaires laminés qui proviennent d'eaux profondes anoxiques. L'assemblage floral et faunique est similaire à celui du Montsech (prov. de Lérida, Espagne), avec des divergences surtout dans les insectes et quelques tétrapodes. Les invertébrés benthoniques sont rares. La plupart des invertébrés sont des arthropodes: trois crustacés et une entomofaune relativement diversifiée. La faune de vertébrés la plus importante est composée par des poissons tant en nombre d'échantillons qu'en diversité (13 taxa différents). Parmi les tétrapodes, le plus abondant est un nouveau genre de Caudata. Les reptiles sont représentés par une tortue, un petit lézard et un crocodile atoposauride. Finalement, un nouvel oiseau est reconnu dans Las Hoyas, avec une position phylogénétique intermédiaire entre Archaeopteryx et les Ornithurae.
Adaptation has been defined and recognized by two different criteria: historical genesis (features built by natural selection for their present role) and current utility (features now enhancing fitness no matter how they arose). Biologists have often failed to recognize the potential confusion between these different definitions because we have tended to view natural selection as so dominant among evolutionary mechanisms that historical process and current product become one. Yet if many features of organisms are non-adapted, but available for useful cooptation in descendants, then an important concept has no name in our lexicon (and unnamed ideas generally remain unconsidered): features that now enhance fitness but were not built by natural selection for their current role. We propose that such features be called
exaptations
and that adaptation be restricted, as Darwin suggested, to features built by selection for their current role. We present several examples of exaptation, indicating where a failure to conceptualize such an idea limited the range of hypotheses previously available. We explore several consequences of exaptation and propose a terminological solution to the problem of preadaptation.
The discovery of a new dentary of “Stenonychosaurus inequalis” with six germ teeth prompted a critical examination of all jaws and teeth attributed to Troodon, Stenonychosaurus, and Pectinodon. It is concluded that Troodon is the senior synonym of these genera, and that the name Troodontidae has priority over Saurornithoididae. Troodontid dentaries are unique amongst the Theropoda in that they lack interdental plates. Previous reports that Dromaeosaurus, Deinonychus, and Saurornitholestes do not have interdental plates are erroneous. Premaxillary, maxillary, anterior dentary and dentary teeth can be distinguished from each other. Each troodontid tooth has a constriction between the crown and root that is more comparable with birds and crocodiles than with other theropods.