Valid Taxon Research Articles

Serendipity at the Smithsonian: The 107-year journey of Rhipidocyrtus muiri Falin & Engel, new genus and species (Ripidiinae, Ripidiini), from jungle beast to valid taxon.

The long and tortuous history of an enigmatic and rare new genus and species of ripidiine wedge beetle (Ripiphoridae: Ripidiinae: Ripidiini) from Borneo is discussed and the taxon described and figured as Rhipidocyrtus muiri Falin & Engel, gen. n. and sp. n. The holotype male, and only known specimen, was collected 107 years ago in Borneo but subsequent to this it was transferred among early researchers in the early 1900s. The specimen was dissected and many portions slide mounted, but these were disassociated from the pinned body for more than a generation. A happenstance encounter led to the rediscovery and reassociation of the body and slide-mounted abdomen and other sclerites in 2011, and to its eventual description herein. Ripidiine diversity is briefly discussed and comparisons made between Rhipidocyrtus and other members of the subfamily.

A taxonomic review of Picumnus exilis (Aves: Picidae) reveals an underestimation of Piculet species diversity in South America

The Picumnus exilis complex is composed of 6–7 subspecies distributed from eastern Colombia, through Venezuela, the Guianas, to northern and northeastern Brazil. They are characterized by a greenish back, whitish or yellowish belly (barred or tainted with black), and males with a red and/or orange forehead. Here we review the taxonomy of this complex based on morphometric and plumage characters from a total of 487 specimens that were analyzed. Eighteen plumage characters were found, of which 12 proved to be informative. The results suggest the existence of five valid taxa: Picumnus exilis (Lichtenstein 1823), a Brazilian endemic found near the coasts of Bahia and Sergipe States; Picumnus pernambucensis Zimmer (1947) another Brazilian endemic occurring north of the Sao Francisco River in the “Pernambuco” Area of Endemism; Picumnus buffonii Lafresnaye (1845) found in the Guiana Shield, east of the Rio Branco and east of the Rio Tocantins on the southern side of the Amazon River; Picumnus undulatus Hargitt (1889) occurring between the Rio Branco, Rio Negro, and Orinoco Rivers, and Picumnus obsoletus Allen (1892) which ranges from the Orinoco Delta north to far northeastern Venezuela. Furthermore, both P. e. salvini Hargitt (1893) and P. nigropunctatus Zimmer and Phelps (1950) proved to be junior synonyms of Picumnus obsoletus Allen (1892). Similarities between the species considered here and other representatives of this genus strongly suggest that the Picumnus exilis complex could also be related to groups of other complexes. This highlights the need for taxonomic reviews to understand the cryptic diversity within the Picumnus genus.

A taxonomic review of the Late Jurassic eucryptodiran turtles from the Jura Mountains (Switzerland and France)

Background. Eucryptodiran turtles from the Late Jurassic (mainly Kimmeridgian) deposits of the Jura Mountains (Switzerland and France) are among the earliest named species traditionally referred to the Plesiochelyidae, Thalassemydidae, and Eurysternidae. As such, they are a reference for the study of Late Jurassic eucryptodires at the European scale. Fifteen species and four genera have been typified based on material from the Late Jurassic of the Jura Mountains. In the past 50 years, diverging taxonomic reassessments have been proposed for these turtles with little agreement in sight. In addition, there has been a shift of focus from shell to cranial anatomy in the past forty years, although most of these species are only represented by shell material. As a result, the taxonomic status of many of these 15 species remains ambiguous, which prevents comprehensive comparison of Late Jurassic turtle assemblages throughout Europe and hinders description of new discoveries, such as the new assemblage recently unearthed in the vicinity of Porrentruy, Switzerland.Methods. An exhaustive reassessment of the available material provides new insights into the comparative anatomy of these turtles. The taxonomic status of each of the 15 species typified based on material from the Late Jurassic of the Jura Mountains is evaluated. New diagnoses and general descriptions are provided for each valid taxon.Results. Six out of the 15 available species names are recognized as valid: Plesiochelys etalloni, Craspedochelys picteti, Craspedochelys jaccardi, Tropidemys langii, Thalassemys hugii, and ‘Thalassemys’ moseri. The intraspecific variability of the shell of P. etalloni is discussed based on a sample of about 30 relatively complete specimens from Solothurn, Switzerland. New characters are proposed to differentiate P. etalloni, C. picteti, and C. jaccardi, therefore rejecting the previously proposed synonymy of these forms. Based partly on previously undescribed specimens, the plastral morphology of Th. hugii is redescribed. The presence of lateral plastral fontanelles is notably revealed in this species, which calls into question the traditional definitions of the Thalassemydidae and Eurysternidae. Based on these new data, Eurysternum ignoratum is considered a junior synonym of Th. hugii. The Eurysternidae are therefore only represented by Solnhofia parsonsi in the Late Jurassic of the Jura Mountains. Finally, ‘Th.’ moseri is recognized as a valid species, although a referral to the genus Thalassemys is refuted.

Revision of the new world species of Hylurgops LeConte, 1876 with the description of a new genus in the Hylastini Coleoptera: Scolytinae) and comments on some Palearctic species.

The New World species of the genus Hylurgops LeConte are revised and Hylurgops subcostulatus Mannerheim is transferred to the new genus Pachysquamus. A revised key to the tribe Hylastini which can be used for the world fauna is presented to include Pachysquamus. Our studies suggest that the Nearctic species H. knausi Swaine is a valid taxon, distinguishable from the Mesoamerican H. planirostris Chapuis. The subspecies H. rugipennis rugipennis Mannerheim and H. r. pinifex Fitch are considered distinct species. A key to Hylurgops species of the New World is provided to accommodate the restituted species. Due to their broadly separated procoxae the Palearctic species H. bonvouloiri and H. inouyei do not agree with the genus Hylurgops.

One or two species? On the case of Hyperolius discodactylus Ahl, 1931 and H. alticola Ahl, 1931 (Anura: Hyperoliidae).

In 1931, Ernst Ahl described two species of reed frogs inhabiting montane forests of the Albertine Rift in East Africa, Hyperolius alticola and H. discodactylus, which were synonymized two decades later by Raymond Laurent. Since then, this revision has been questioned repeatedly, but taxonomists have been reluctant to make a conclusive decision on the matter, especially since the type material of H. alticola was reported as being lost. Here, we examine the rediscovered type material of H. alticola and reassess the validity of Laurent's synonymy using morphological data from historic and new collections including all available type material, call recordings and molecular data from animals collected on recent expeditions. We find evidence for a northern and southern genetic clade, a divide that is somewhat supported by diverging morphology as well. However, no distinction in advertisement calls could be recovered to support this split and both genetic and morphological differences between geographic units are marginal and not always congruent and thus more likely reflect population-level variation. We therefore conclude that H. alticola is not a valid taxon and should continue to be treated as a synonym of H. discodactylus. Finally, we also report on newly collected material from outside the species known range, with first records of this species from Burundi.

Phylogenetic reassessment ofLourinhasaurus alenquerensis, a basal Macronaria (Sauropoda) from the Upper Jurassic of Portugal

Lourinhasaurus alenquerensis is a Portuguese Upper Jurassic dinosaur whose lectotype is one of the most complete sauropod specimens from the Portuguese fossil record and from the Upper Jurassic of Europe. It was recovered from sediments of the Sobral Formation (upper Kimmeridgian to lower Tithonian) at Moinho do Carmo (Alenquer, Portugal). The lectotype of Lourinhasaurus was first related to Apatosaurus and then tentatively related to Camarasaurus. Finally, it was established as a new taxon, Lourinhasaurus, including the Moinho do Carmo specimen. At the time of writing, Lourinhasaurus had a poor diagnosis and an unstable phylogenetic position. Revision of the Moinho do Carmo specimen has led to a detailed description and a new and more complete codification for several morphological characters. The phylogenetic analyses proposed herein considered Lourinhasaurus as a Camarasauromorpha Macronaria. This study also recovered a Camarasauridae clade incorporating Lourinhasaurus, Camarasaurus and, putatively, Tehuelchesaurus and that implies the presence of Camarasauridae in the European Upper Jurassic. Besides the strong similarity to Camarasaurus, Lourinhasaurus alenquerensis is here considered a valid taxon with 13 putative autapomorphies such as a sagittal keel on the dorsal margin of sacral neural spines, circular and deep spinoprezygapophyseal fossa on proximal caudal vertebrae, marked crest and groove bordering the lateral margin of the acetabulum in the ischium, and a marked deflection of the entire femoral shaft without lateral bulge. The apparently high number of taxa among the sauropod fauna from the Iberian Peninsula during the Late Jurassic is similar to the palaeobiodiversity recorded in formations of the same age, i.e. Morrison and Tendaguru, and does not support the hypothesis of a connection between the North America and Iberian Peninsula faunas during the later part of the Late Jurassic reflected by other faunal and floral groups. © 2014 The Linnean Society of London

Redescription of Cearadactylus atrox (Pterosauria, Pterodactyloidea) from the Early Cretaceous Romualdo Formation (Santana Group) of the Araripe Basin, Brazil

ABSTRACT Based on one of the first cranial pterosaur specimens unearthed from the Romualdo Formation (Araripe Basin), Cearadactylus atrox has caused disagreement among paleontologists regarding its relationships. Ranging from an ornithocheirid, an indeterminated pterodactyloid, to a ctenochasmatid, some authors even regarded this species as representing a distinct suprageneric clade. Further preparation of the holotype that was transferred to the collections of the Museu Nacional/UFRJ (MN 7019-V) revealed several new features allowing a redescription and reevaluation of the phylogenetic position of this species. Among the new observations, it is clear that the rostral end of this specimen had been glued to the skull, rendering previous anatomical interpretations incorrect. There is no rostral gap, and the expanded rostral end of the premaxillae is larger than the dentary, rather than smaller. Cearadactylus atrox is here considered a valid taxon that can be diagnosed by a dentary groove that bifurcates at the rostral end, orbit and naris in a high position relative to the nasoantorbital fenestra, and a comparatively small number of teeth (32–36 maxillary, 22–26 mandibular), decreasing in size towards the posterior end. Phylogeneticaly, it is placed as the sister group of the Anhangueridae, forming a large clade of Brazilian forms (Tropeognathus and Anhanguera), which has a European taxon (‘Ornithocheirus’ compressirostris) as its sister group. SUPPLEMENTAL DATA—Supplemental materials are available for this article for free at www.tandfonline.com/UJVP

Review ofAcutipulaCrane Flies of Taiwan, with Descriptions of New Species and Immature Instars (Diptera: Tipulidae: Tipulinae:Tipula)

ABSTRACT Taiwanese species of the crane fly subgenus Tipula (Acutipula) Alexander, 1924, are reviewed. Six species are recognized with two species being newly described: T. (A.) barbigeraand T. (A.) furcifera, both from Nantou. Tipula (A.) shirakii Edwards, 1916, previously considered a synonym of T. (A.) quadrinotata Brunetti, 1912, is recognized as a valid taxon. The female of T. (A.) kuzuensis Alexander, 1918, is described for the first time. DNA barcode sequences for 12 species of T. (Acutipula) are investigated and maximum likelihood trees resulting from the analyses are presented. The external anatomy of the last instar larva and pupa of T. (A.) shirakii is described and illustrated. Comments concerning the biology and habitats of larvae are presented. A taxonomic key is provided to identify all species recorded in Taiwan, and their distributions are briefly discussed.

Redescription of the phytosaursPaleorhinus(‘Francosuchus’)angustifronsandEbrachosuchus neukamifrom Germany, with implications for Late Triassic biochronology

Phytosaurs are a diverse and morphologically distinctive clade of superficially crocodile-like archosauriforms that had a near global distribution during the Late Triassic. Because their remains are among the most abundant vertebrate remains recovered in many Upper Triassic terrestrial formations, phytosaurs are used extensively in long-range biochronological and biostratigraphic correlations. The biochronologically oldest and earliest branching known phytosaurs include an array of nominal species from the early Late Triassic of the United States, Germany, Poland, Morocco, and India that have been synonymized within the genus Paleorhinus, and subsequently used to define a global ‘Paleorhinus biochron’. However, recent phylogenetic work suggested that the North American species previously referred to Paleorhinus are paraphyletic. Here, we reassess the systematics and anatomy of putative specimens of Paleorhinus from southern Germany. Two well-preserved basal phytosaur skulls from the Blasensandstein (Carnian) of Bavaria form the holotypes of Francosuchus angustifrons and Ebrachosuchus neukami, both of which were synonymized with Paleorhinus by previous workers. We demonstrate that Francosuchus angustifrons shares unique synapomorphies with specimens referred to Paleorhinus bransoni from the Late Triassic of Texas, and thus refer the species to Paleorhinus. By contrast, the longirostrine Ebrachosuchus is highly distinctive in morphology, and our new cladistic analysis of Phytosauria demonstrates that it represents a valid taxon that is more closely related to Phytosauridae than to Paleorhinus. We provide the first autapomorphy-based support for a monophyletic but restricted Paleorhinus (supported by a nodal row on the jugal, and low paired ridges on the squamosal) and confirm that previous broader conceptions of Paleorhinus are likely to be paraphyletic. © 2013 The Linnean Society of London

The Status ofPlethodon ainsworthiLazell: Extinct, Extant, or Nonexistent?

Plethodon ainsworthi Lazell was described as a new species in the slimy salamander (Plethodon glutinosus [Northern Slimy Salamander]) complex from two specimens collected in Jasper County, MS, in 1964. Prior to their designation as the type and paratype of the newly described species in 1998, both specimens were presumably stored in strong formalin for 26 years and thus were in poor condition. Plethodon ainsworthi is distinguished from the sympatric Plethodon mississippi (Mississippi Slimy Salamander) by a more attenuated body, as evidenced by a higher snout-vent length (SVL)/head width (HW) ratio, and shorter limbs. Despite numerous searches between 1991 and 1997, no subsequent specimens of P. ainsworthi were found. As a result, P. ainsworthi is the only modern-day amphibian in the United States to be declared extinct by the IUCN. In 2000 and 2001, we searched the presumed location of the type specimens of P. ainsworthi for additional specimens. Although we located slimy salamanders, we did not find any specimens with noticeably attenuated bodies or short limbs. We then compared SVL/HW ratios between the two specimens of P. ainsworthi, 24 specimens of slimy salamanders that we collected in Jasper County from or near the collection site of P. ainsworthi, and 50 museum specimens of P. mississippi collected from six counties in Mississippi outside of Jasper County. The upper limit of the SVL/HW ratio for some of the specimens we collected, as well as for some of the museum specimens of P. mississippi, was considerably higher than the 7.2 reported for P. mississippi by Lazell (1998). In addition, we found overlap in SVL/HW ratios between P. ainsworthi and one specimen of P. mississippi, although this individual did not have short limbs. The distinct morphology of P. ainsworthi may be the consequence of the long-term, improper preservation of specimens of P. mississippi. Our results provide compelling evidence that P. ainsworthi is not a valid taxon.

Is Torosaurus Triceratops? Geometric Morphometric Evidence of Late Maastrichtian Ceratopsid Dinosaurs

BackgroundRecent assessments of morphological changes in the frill during ontogeny hypothesized that the late Maastrichtian horned dinosaur Torosaurus represents the “old adult” of Triceratops, although acceptance of this finding has been disputed on several lines of evidence.Methodology/Principal FindingsExamining the cranial morphology of 28 skulls in lateral view and 36 squamosals of Nedoceratops hatcheri, Triceratops spp. and Torosaurus spp. by means of landmark-based geometric morphometrics, we compared ontogenetic trajectories among these taxa. Principal Component Analysis and cluster analysis confirmed different cranial morphologies. Torosaurus shape space is well separated from Triceratops, whereas Triceratops horridus and Triceratops prorsus partially overlap within Triceratops shape space. Linear regressions between shape and size suggest different ontogenetic trajectories among these taxa. Results support the “traditional” taxonomic status of Torosaurus. We hypothesize that ontogeny drives cranial morphology with different patterns between Torosaurus and Triceratops.Conclusions/Significance Torosaurus is a distinct and valid taxon. Whether looking at entire skulls, skulls without the frill, frills alone, or squamosals, Torosaurus has different morphologies and distinct allometric trajectories compared to Triceratops. This new approach confirms the taxonomic status of Torosaurus as well as the comparatively low diversity of ceratopsids at the end of the Maastrichtian in North America.

Genetic variation corroborates subspecific delimitation in the Namib fog-basking beetle, Onymacris unguicularis (Haag) (Tenebrionidae, Coleoptera)

The fog-basking beetle, Onymacris unguicularis (Haag, 1875), is currently listed as a polytypic form comprising two subspecies. A flightless substrate specialist, the beetleis endemic to vegetationless dunes in the Namib, where southern populations constitute the nominate subspecies, O. u. unguicularis, and populations some 300 km to the north compose O. u. schulzeae Penrith, 1984. Their taxonomic descriptions are based on minor differences in pronotal and prosternal shape, and the phylogenetic validity of these subspecies has yet to be ascertained. Here we reassess the polytypic status of O. unguicularis by (1) examining diagnostic phenotypic characters in conjunction with a geometric morphometric analysis, and (2) conducting phylogenetic analysis of mitochondrial DNA sequences. Our results confirm pronotal and prosternal differences, which are complemented by geometric morphometric resolution of the subspecies. Phylogenetic analysis recovered two reciprocally monophyletic lineages that exhibit perfect phylogeographic congruence with phenotypic variation. Our genetic data identify southern and northern populations as distinct lineages, corroborate morphometric data regarding subspecific delimitation, and therefore support the recognition of O. u. unguicularis and O. u. schulzeae as valid taxa under the general lineage concept.

Anatomy and phylogenetic relationships of Calamops paludosus (Temnospondyli, Stereospondyli) from the Triassic of the Newark Basin, Pennsylvania

ABSTRACT The holotype of the large temnospondyl Calamops paludosus is the oldest known tetrapod fossil from the Triassic of the Newark basin in Pennsylvania. Although it is usually placed in Metoposauridae, its affinities have remained unknown since its original description because the unique specimen had never been prepared. Preparation and casting of the specimen, which comprises three pieces of a left mandibular ramus, now permits detailed anatomical description of the jaw and assessment of its affinities. Calamops paludosus is a valid taxon of trematosauroid temnospondyls that can be diagnosed by several autapomorphies. It represents one of the geologically youngest known records of long-snouted trematosaurs and the first record of these temnospondyls from the Late Triassic of North America. SUPPLEMENTAL DATA—Supplemental materials are available for this article for free at www.tandfonline.com/UJVP

"Forms" of water mites (Acari: Hydrachnidia): intraspecific variation or valid species?

In many groups of organisms, especially in the older literature, it has been common practice to recognize sympatrically occurring phenotypic variants of a species as “forms”. However, what these forms really represent often remains unclear, especially in poorly studied groups. With new algorithms for DNA-based species delimitation, the status of forms can be explicitly tested with molecular data. In this study, we test a number of what is now recognized as valid species of water mites (Hydrachnidia), but have in the past been treated as forms sympatrically occurring with their nominate species. We also test a form without prior taxonomical status, using DNA and morphometrics. The barcoding fragment of COI, nuclear 28S and quantitative analyses of morphological data were used to test whether these taxa merit species status, as suggested by several taxonomists. Our results confirm valid species. Genetic distances between the form and nominate species (Piona dispersa and Piona variabilis, COI 11%), as well as likelihood ratio tests under the general mixed-Yule coalescent model, supported that these are separately evolving lineages as defined by the unified species concept. In addition, they can be diagnosed with morphological characters. The study also reveals that some taxa genetically represent more than one species. We propose that P. dispersa are recognized as valid taxa at the species level. Unionicola minor (which may consist of several species), Piona stjordalensis, P. imminuta s. lat., and P. rotundoides are confirmed as species using this model. The results also imply that future studies of other water mite species complexes are likely to reveal many more genetically and morphologically distinct species.

Discovery of Recent thecideide brachiopods (Order: Thecideida, Family: Thecideidae) in Sulawesi, Indonesian Archipelago, with implications for reproduction and shell size in the genus Ospreyella.

For the first time thecideide brachiopods have been discovered in the Indonesian Archipelago. All specimens were collected in a water depth of 30 m from an old shipwreck, the "Mutiara", which represents a remarkable habitat for these cryptic brachiopods despite its artificial nature. The thecidellinine species Minutella cf. minuta and the lacazelline species Ospreyella mutiara n. sp. are described and illustrated comprehensively, including their shell ontogeny. The inclusion of the new species O. mutiara in the genus Ospreyella Lüter and Wörheide, 2003 is based on results of an integrated approach combining morphological, ontogenetic and genetic studies. Relevant morphological characters diagnostic for Ospreyella are established. In addition, all Recent lacazelline brachiopod genera are confirmed as valid taxa using molecular methods. The small body size of 0. mutiara and the weakly developed brachidium in comparison to other Ospreyella species as a consequence of heterochrony is discussed in more detail. O. mutiara is the first species of the exclusively gonochoristic genus Ospreyella for which hermaphroditism is now documented.

Phytoplasma infection in prized linden Tilia platyphyllos var. laciniata: is 'laciniata' a valid botanical variety?

Linden (Tilia platyphyllos var. laciniata) trees growing in Kaunas Botanical Garden and in the parks of Verkiu (Vilnius) and Belvederis estates in Lithuania exhibit laciniated, deformed leaves and yellowing of the veins. These trees had been planted in the parks, for the beauty of their “cut-out-elongated leaves”, as a new variety of linden. However, use of the polymerase chain reaction (PCR), primed by phytoplasma universal primer pairs to amplify 16S rRNA gene sequences, followed by restriction fragment length polymorphism (RFLP) analysis, revealed that these linden trees were infected by phytoplasma strains belonging to subgroup 16SrI-B and to a new subgroup designated 16SrI-V, in the ‘Candidatus Phytoplasma asteris’ species of wall-less bacteria. The strains were further characterized by ribosomal protein gene sequence analysis. The experimental results have rekindled discussion of the possibility that a prized cultivar displaying unusual morphotype might be an invalid taxon. Is linden with laciniate-leaved branches a valid taxon (botanical variety), or simply a plant that has abnormal leaf morphotype caused by infection with a tiny wall-less bacterium?

Annotated checklist of Capitellidae (Annelida, Polychaeta) from the Iberian Peninsula, Chafarinas, Balearic and Canary Islands

The present annotated checklist has been elaborated after revision of preserved materials (from the Museo Nacional de Ciencias Naturales, Madrid and the reference collection of the Marine Biology Laboratory of the University of Valencia) and published literature related to capitellids from the Iberian Peninsula, Chafarinas, Balearic and Canary Islands. Twenty-four species and subspecies belonging to thirteen genera are recognized as valid taxa. With this checklist we include some taxonomic details and information on distribution at both global and regional levels. This work includes the setal formula and diagrammatic representation of capitellid taxa treated in this study.

A reevaluation ofSigilmassasaurus brevicollis(Dinosauria) from the Cretaceous of Morocco

The original hypodigm of the controversial mid-Cretaceous Moroccan dinosaur Sigilmassasaurus brevicollis is redescribed, and the diagnosis of the taxon is revised. Unambiguously referred material is restricted to cervical and anterior dorsal vertebrae sharing apomorphies with the holotype. A newly recognized diagnostic character of Sigilmassasaurus is the absence of anterior and posterior interzygapophyseal laminae of the neural arch, so that the neural spine directly meets the dorsal margin of the neural canal. A phylogenetic analysis supports the inclusion of Sigilmassasaurus in Tetanurae but not in Carcharodontosauridae. Sigilmassasaurus is distinct from all other theropods known from comparable material and is thus retained as a valid taxon.

On the validity and phylogenetic position of Eubrachiosaurus browni, a kannemeyeriiform dicynodont (Anomodontia) from Triassic North America.

The large dicynodont Eubrachiosaurus browni from the Upper Triassic Popo Agie Formation of Wyoming is redescribed. Eubrachiosaurus is a valid taxon that differs from Placerias hesternus, with which it was previously synonymized, by greater anteroposterior expansion of the scapula dorsally and a very large, nearly rectangular humeral ectepicondyle with a broad supinator process. Inclusion of Eubrachiosaurus in a revised phylogenetic analysis of anomodont therapsids indicates that it is a stahleckeriid closely related to the South American genera Ischigualastia and Jachaleria. The recognition of Eubrachiosaurus as a distinct lineage of North American dicynodonts, combined with other recent discoveries in the eastern USA and Europe, alters our perception of Late Triassic dicynodont diversity in the northern hemisphere. Rather than being isolated relicts in previously therapsid-dominated regions, Late Triassic stahleckeriid dicynodonts were continuing to disperse and diversify, even in areas like western North America that were otherwise uninhabited by coeval therapsids (i.e., cynodonts).

Skeletal morphology of Kritosaurus navajovius (Dinosauria: Hadrosauridae) from the Late Cretaceous of the North American south-west, with an evaluation of the phylogenetic systematics and biogeography of Kritosaurini

The osteology of the hadrosaurid dinosaur Kritosaurus navajovius (late Campanian of southern North America) is documented in detail, and the taxonomy and phylogenetic relationships of the genus are revised. Kritosaurus is rediagnosed based on the extensive length of the dorsolateral margin of the maxilla and a unique combination of characters that includes a jugal with orbital constriction deeper than infratemporal one, infratemporal fenestra greater than orbit and with dorsal margin greatly elevated above dorsal orbital margin in adults, frontal participating in orbital margin, and paired caudal parasagittal processes of nasals resting over frontals. The taxonomy of numerous hadrosaurid specimens previously referred to Kritosaurus is reassessed; the vast majority of these cannot be positively referred to Kritosaurus. One exception is a specimen collected from the Cerro del Pueblo Formation that extends the geographical range of K. navajovius further south in Laramidia, to present-day northern Mexico. Anasazisaurus is regarded a junior synonym of Kritosaurus; their holotypes are indistinguishable from each other when considering the overlapping elements. However, many characters support distinction of Naashoibitosaurus ostromi as a valid taxon. Kritosaurus, consisting of the sister species K. navajovius and K. horneri, is deeply nested within Saurolophinae as a member of Kritosaurini. The latter clade includes also Naashoibitosaurus, Gryposaurus, and the South American Secernosaurus. Kritosaurini is characterized by a rostral nasal dorsal process not reaching the rostral margin of the narial foramen, frontal with triangular rostrolateral projection ending in a narrow apex (convergent in Brachylophosaurini), and a subrectangular dorsal region of infratemporal fenestra, among other characters. Kritosaurin hadrosaurids are hypothesized to have originated in southern Laramidia no later than the early Campanian. Subsequently, members of the clade reached northern Laramidia and South America via dispersal no later than the early and late Campanian, respectively.