Dermal Spines Research Articles

New Fossils of Stegosaurs from the Upper Jurassic of the Eastern Iberian Peninsula (Spain)

The eastern Iberian Peninsula is one of the places with most stegosaur fossils in all of Europe. In the present study, we describe new remains from six different fossil sites from the Upper Jurassic of the Villar del Arzobispo Formation (Kimmeridgian–Tithonian). The remains comprise: a left humerus from CT-61 (El Castellar, Teruel), a dermal spine from Puntal de la Magdalena (Alpuente, Valencia), two caudal neural arches and five caudal vertebrae from Cañada París (Alpuente, Valencia), two caudal centra from Alpuente (Valencia) and four caudal vertebrae from Barrihonda-El Humero (Riodeva, Teruel). The left humerus (CT-61-1) and dermal spine (MPA D-110) are referred to Stegosauria indet. The caudal vertebrae from Alpuente (Cañada París specimen, MPA-653 and MPA D-1086) are referred to cf. Dacentrurus sp. Finally, the caudal vertebrae from Riodeva (Barrihonda-El Humero specimen) are referred to Dacentrurus armatus and assigned to a previously known caudal series from this site. The presence of abundant localities with stegosaurian remains reaffirms the important role of stegosaur dinosaurs in Late Jurassic coastal ecosystems.

The fossil record of the Bramble-shark Echinorhinus (Echinorhiniformes, Echinorhinidae) in South America

The present contribution aims is to analyze the fossil record of the genus Echinorhinus in South America, and particularly Argentina. We made a first-hand examination of the species Echinorhinus pozzi from the early Miocene of Patagonia, and recognize it as a valid taxon. The species was originally described in the XIX century, and since then no author described or illustrated the original material based on observations of the actual specimens. The genus Echinorhinus is reported for the first time in late Miocene Paraná beds, based on the occurrence of fossil dermal spines. The species Echinorhinus maremagnum occurring in the latest Cretaceous outcrops from Patagonia in Chile and Argentina is considered valid and clearly distinguishable from E. lapaoi, contradicting recent claims that argue their synonymy.

Reproductive biology and sexual dimorphism of the poorly known frog Chiasmocleis alagoana (Microhylidae, Gastrophryninae), with an updated diagnosis for the species

ABSTRACT Chiasmocleis is the most species-rich New World microhylid genus. Among Atlantic Forest species in the genus, C. alagoana has the northernmost distribution. The species was described two decades ago; however, little is known about its natural history. Herein, we provide information on its reproductive biology, advertisement call, and external morphology based on specimens from the type locality and the type series. Reproduction occurs in the rainy season but only on days with torrential rains. The advertisement call consists of a series of pulsed notes common for most species of the genus. Structurally, each note consists of two groups of distinct pulses with amplitude modulations. This call structure is a candidate of synapomorphy for a subclade of the genus consisting of C. alagoana, C. cordeiroi, C. crucis, and C. schubarti. Morphologically, the species exhibit sexual dimorphism with females being larger and twice heavier than males. Both sexes have fringes on fingers and toes. Moreover, we report the presence of dermal spines over the body and webbing on feet in males and include these characters in an update diagnosis of the species.

Evolution and Developmental Diversity of Skin Spines in Pufferfishes.

SummaryTeleost fishes develop remarkable varieties of skin ornaments. The developmental basis of these structures is poorly understood. The order Tetraodontiformes includes diverse fishes such as the ocean sunfishes, triggerfishes, and pufferfishes, which exhibit a vast assortment of scale derivatives. Pufferfishes possess some of the most extreme scale derivatives, dermal spines, erected during their characteristic puffing behavior. We demonstrate that pufferfish scale-less spines develop through conserved gene interactions that underlie general vertebrate skin appendage formation, including feathers and hair. Spine development retains conservation of the EDA (ectodysplasin) signaling pathway, important for the development of diverse vertebrate skin appendages, including these modified scale-less spines of pufferfish. Further modification of genetic signaling from both CRISPR-Cas9 and small molecule inhibition leads to loss or reduction of spine coverage, providing a mechanism for skin appendage diversification observed throughout the pufferfishes. Pufferfish spines have evolved broad variations in body coverage, enabling adaptation to diverse ecological niches.

From Scale to Spine: Evolution and Developmental Diversity of Skin Spines in Pufferfishes

Teleost fishes develop a remarkable variety of skin ornaments. However, the developmental basis of these structures is poorly understood. The teleost order Tetraodontiformes includes diverse fishes such as the ocean sunfishes, triggerfishes and pufferfishes, which exhibit a vast assortment of scale derivatives. Pufferfishes and porcupine fishes possess some of the most extreme scale derivatives, dermal spines, which are erected during their characteristic puffing behavior. Here, we focus on pufferfishes and demonstrate that the spines develop through conserved gene interactions that underlie skin appendage formation throughout other vertebrates, including avian feathers and mammalian hair. Pufferfish spine development retains the conserved role of the EDA (ectodysplasin) signaling pathway, suggesting that EDA is an important molecule/pathway for the development of diverse vertebrate skin appendages, including these modified scale-less spines of the pufferfish lineage. Further modification of genetic signaling from both CRISPR-Cas9 and small molecule inhibition can lead to both loss or reduction of spine coverage in pufferfish, providing a mechanism for skin appendage diversification observed in the extant clade of pufferfishes (Tetraodontidae). Dermal spines are unique scale-derivatives that evolved through conserved gene network modification. In pufferfish they exhibit broad variation in coverage, enabling adaptation to diverse ecological niches.

Vascularization and odontode structure of a dorsal ridge spine of Romundina stellina Ørvig 1975.

There are two types of dermal skeletons in jawed vertebrates: placoderms and osteichthyans carry large bony plates (macromery), whereas chondrichthyans and acanthodians are covered by small scales (micromery). Fin spines are one of the last large dermal structures found on micromeric taxa and offer a potential source of histology and morphology that can be compared to those found on macromeric groups. Dermal fin spines offer a variety of morphology but aspects of their growth modes and homology are unclear. Here, we provide detailed descriptions of the microstructure and growth of a dorsal ridge spine from the acanthothoracid placoderm, Romundina stellina, using virtual three-dimensional paleohistological datasets. From these data we identify several layers of dentine ornamentation covering the lateral surfaces of the spine and reconstructed their growth pattern. We show that this spine likely grew posteriorly and proximally from a narrow portion of bone located along the leading edge of the spine. The spine is similarly constructed to the scales with a few exceptions, including the absence of polarized fibers distributed throughout the bone and the presence of a thin layer of perichondral bone. The composition of the spine (semidentine odontodes, dermal bone, perichondral bone) is identical to that of the Romundina dermal plates. These results illustrate the similarities and differences between the dermal tissues in Romundina and indicate that the spine grew differently from the dentinous fin spines from extant and fossil chondrichthyans. The morphology and histology of Romundina is most similar to the fin spine of the probable stem osteichthyan Lophosteus, with a well-developed inner cellular bony base and star-shaped odontodes on the surface. Results from these studies will undoubtedly have impact on our understanding of fossil fin spine histology and evolution, contributing to the on-going revision of early gnathostome phylogeny.

Purported earliest bones of a plated dinosaur (Ornithischia: Stegosauria): a "dermal tail spine" and a centrum from the Aalenian-Bajocian (Middle Jurassic) of England, with comments on other early thyreophorans

Purported earliest bones of a plated dinosaur (Ornithischia: Stegosauria): a "dermal tail spine" and a centrum from the Aalenian-Bajocian (Middle Jurassic) of England, with comments on other early thyreophorans

Pectoral Morphology inDoliodus: Bridging the ‘Acanthodian’-Chondrichthyan Divide

ABSTRACT Doliodus problematicus (NBMG 10127), from the Lower Devonian of New Brunswick, Canada (approx. 397–400 Mya) is the earliest sharklike jawed vertebrate (gnathostome) in which the pectoral girdle and fins are well preserved. Its pectoral endoskeleton included sharklike expanded paired coracoids, but Doliodus also possessed an “acanthodian-like” array of dermal spines, described here for the first time. Doliodus provides the strongest anatomical evidence to date that chondrichthyans arose from “acanthodian” fishes by exhibiting an anatomical mosaic of “acanthodian” and sharklike features.

Molecular and morphological data reveal three new cryptic species of Chiasmocleis (Mehely 1904) (Anura, Microhylidae) endemic to the Atlantic Forest, Brazil.

Three new cryptic species of Chiasmocleis from the Atlantic Forest of Brazil are described. Two of these species occur in the northeastern states of Sergipe and Bahia, whereas the third species is found in the southeastern state of São Paulo. The new species can be distinguished from other congeneric species by the molecular data, as evidenced in the phylogeny, and by a combination of morphological characters including: size, foot webbing, dermal spines, and coloration patterns. Chiasmocleis species differ in osteological traits, therefore we also provide an osteological description of each new species and comparsions with data reported for other species in the genus.

Multiple anti‐predator mechanisms in the red‐spotted Argentina Frog (Amphibia: Hylidae)

AbstractAnurans employ a wide variety of anti‐predator mechanisms to defend themselves. In casque‐headed hylids, defence is thought to be a complex combination of several anti‐predator mechanisms. However, the defence traits of only a few species are known; some hypotheses have yet to be addressed, whereas others, already tested in some species, need to be tested in additional taxa. The anti‐predator mechanism of the casque‐headed frog, Argenteohyla siemersi, is described here. It is a complex mechanism consisting of (1) behavioural and ecological traits, including secretive and semi‐phragmotic habits and posture; (2) morphological features, including cryptic and aposematic colourations, a skull covered with bony dermal spines and protuberances that are associated with two types of granular venom glands; and (3) physiological and chemical traits, such as a highly lethal skin secretion. Our results are compared with those of previous studies of defence mechanisms in casque‐headed frogs in an effort to understand the mechanisms and evaluate their potential phylogenetic signal in this group of anurans.

Reassessment of the earliest documented stegosaurian fossils from Asia

In 1929, the famous Swedish palaeontologist Carl Wiman documented the first unequivocal stegosaurian dinosaur fossils from Asia. His material comprised an isolated dermal spine, together with a dorsal vertebra that was briefly described but never figured. Since then these remains have languished in obscurity, being noted in some stegosaur review articles but often ignored altogether. However, recent auditing of the Museum of Evolution palaeontological collection at Uppsala University in Sweden has led to the rediscovery of Wiman's original specimens, as well as two additional previously unrecognised stegosaurian dorsal vertebrae. All of these bones derive from the Lower Cretaceous (Berriasian–Valanginian) Mengyin Formation of Shandong Province in eastern China, and are morphologically compatible with the stratigraphically proximal stegosaurian taxon Wuerhosaurus from the Valanginian–Albian Tugulu Group in the Xinjiang Uyghur Autonomous Region of Western China. Wiman's seminal stegosaurian fossils thus expand current palaeobiogeographical distributions, and contribute to the otherwise enigmatic record of Early Cretaceous stegosaurian occurrences globally.

The origins of adipose fins: an analysis of homoplasy and the serial homology of vertebrate appendages

Adipose fins are appendages found on the dorsal midline between the dorsal and caudal fins in more than 6000 living species of teleost fishes. It has been consistently argued that adipose fins evolved once and have been lost repeatedly across teleosts owing to limited function. Here, we demonstrate that adipose fins originated repeatedly by using phylogenetic and anatomical evidence. This suggests that adipose fins are adaptive, although their function remains undetermined. To test for generalities in the evolution of form in de novo vertebrate fins, we studied the skeletal anatomy of adipose fins across 620 species belonging to 186 genera and 55 families. Adipose fins have repeatedly evolved endoskeletal plates, anterior dermal spines and fin rays. The repeated evolution of fin rays in adipose fins suggests that these fins can evolve new tissue types and increased structural complexity by expressing fin-associated developmental modules in these new territories. Patterns of skeletal elaboration differ between the various occurrences of adipose fins and challenge prevailing hypotheses for vertebrate fin origin. Adipose fins represent a powerful and, thus far, barely studied model for exploring the evolution of vertebrate limbs and the roles of adaptation and generative biases in morphological evolution.

A new species of Stereocyclops Cope (Anura, Microhylidae) from Southeastern Brazil

A new species of Stereocyclops is described from the Zona da Mata Regional Airport (21o 31’S, 43o 11’W; 408 m a.s.l.),Municipality of Goianá, State of Minas Gerais, Southeastern Brazil. Stereocyclops palmipes sp. nov. is characterized by itsmedium size (SVL 43.7–48.5 mm in males; SVL 48.4–56.7 mm in females); in males, large, numerous dermal spinesconcentrated in the inferior border of mandible, forming a band; dermal spines scattered on ventral surfaces of body, arms,fingers, legs, toes, and pericloacal region of males, and agglomerate only in pericloacal region and ventral surfaces of thighs infemales; fringes and interdigital membranes of toes developed; color pattern composed by two mid-dorsal, poorly defined, dark brown stripes from the inguinal regions to head, passing on the occipital dermal fold and reaching the upper eyelid.

A new genus and species of surgeon fish (Perciformes, Acanthuridae) from the Oligocene of Kanton Glarus, Switzerland

The new genus and species of surgeon fish, Glarithurus friedmani (Acanthuridae), from the Lower Oligocene (Rupelian) of Kanton Glarus, Switzerland, differs from all other acanthurid fishes, fossil and extant, by having a single anal-fin basal pterygiophore situated in the first interhaemal space, versus two or more such pterygiophores in all other taxa. The new taxon is based upon a 29-mm SL acronurus stage specimen that probably had already settled onto a benthic substrate from its pelagic larval stage and begun its transformation into a juvenile. It has a scalpel-like dermal spine on the caudal peduncle and a crest on the hyomandibular, which are derived characters that establish it as a member of the clade of higher acanthurins. Within that clade, it is unique because of the great depth of its basipterygium at the subpelvic keel.

Redescription and variation of Hyophryne histrio Carvalho, 1954, an enigmatic microhylid frog from the Atlantic Rainforest of Brazil

Abstract Hyophryne histrio was described in 1954 as a new species and placed in its own genus based on a single juvenile specimen from Ilhéus, State of Bahia, northeastern Brazil. This species was known only from the holotype until 1999 when a series of specimens was collected 50 km from the type-locality. Herein, we provide a redescription of the species based on this new material and present new information on morphological variation in order to help with the recognition of this poorly known species. The diagnostic characters are: occipital skin fold present, interdigital membranes between the toes well developed, dark venter with white blotches, an arrow-shaped dorsal color pattern that begins just after the occipital fold, and a distinct pale line between the venter and dorsum. Dermal spines, which were found in all males and vary in the number of spines and location, are reported for the first time in this species; gravid females have dermal spines only in the pericloacal region. We also compare Hyophryne histrio to all other Neotropical microhylid genera.

New stegosaurian (Ornithischia, Thyreophora) remains from Jurassic-Cretaceous transition beds of Valencia province (Southwestern Iberian Range, Spain)

New stegosaurian remains have been recently recovered from the Jurassic-Cretaceous transition sandstones of the Villar del Arzobispo Formation (Tithonian-Berriasian) in the Valencia province, eastern Spain. Specimens consist of two partially articulated (or closely associated) postcranial skeletons. The Baldovar specimen is composed of appendicular bones (scapula, femur) and two pairs of dermal tail spines, two of them articulated with two distal caudal vertebrae. The second specimen, unearthed in the vicinity of La Yesa village, consists of dorsal vertebrae and ribs, fragments of caudal centra and an incomplete femur. The new specimens are tentatively referred to the clade Dacentrurinae and may belong to Dacentrurus on the basis of features observed on the dorsal vertebrae and caudal dermal spines. Stegosaurs are represented so far in the Jurassic-Cretaceous transition of Spain by Dacentrurus. The presence of other taxa (Stegosaurus, Miragaia) in Spain, recently documented in the Late Jurassic of Portugal, cannot be attested on the basis of the currently recorded material.

New stegosaurian (Ornithischia, Thyreophora) remains from Jurassic-Cretaceous transition beds of Valencia province (Southwestern Iberian Range, Spain)

New stegosaurian remains have been recently recovered from the Jurassic-Cretaceous transition sandstones of the Villar del Arzobispo Formation (Tithonian-Berriasian) in the Valencia province, eastern Spain. Specimens consist of two partially articulated (or closely associated) postcranial skeletons. The Baldovar specimen is composed of appendicular bones (scapula, femur) and two pairs of dermal tail spines, two of them articulated with two distal caudal vertebrae. The second specimen, unearthed in the vicinity of La Yesa village, consists of dorsal vertebrae and ribs, fragments of caudal centra and an incomplete femur. The new specimens are tentatively referred to the clade Dacentrurinae and may belong to Dacentrurus on the basis of features observed on the dorsal vertebrae and caudal dermal spines. Stegosaurs are represented so far in the Jurassic-Cretaceous transition of Spain by Dacentrurus. The presence of other taxa (Stegosaurus, Miragaia) in Spain, recently documented in the Late Jurassic of Portugal, cannot be attested on the basis of the currently recorded material.

A new species of narrow-mouthed frog of the genus Chiasmocleis Méhelÿ 1904 (Anura, Microhylidae) from the Amazonian rainforest of Brazil

A new species of microhylid frog of the genus Chiasmocleis from the Amazonian rainforest of northern Brazil, in the states of Amazonas, Mato Grosso, Pará and Rondônia, is described and illustrated. The new species is characterized by the combination of: large size for the genus; robust body; finger I well developed; toe I developed; toes of males extensively webbed, of females basally webbed; toes fringed; dermal spines on the anterior portion of chin in males. An osteological description and brief notes on natural history are also given. Tadpole and advertisement call are unknown. The species was found in several herpetological collections misidentified as Chiasmocleis bassleri, C. shudikarensis or C. ventrimaculata, and a comparison with those species and comments on the taxonomy of the genus are provided.

Descriptions of two new Spinomantis frogs from Madagascar (Amphibia: Mantellidae), and new morphological data for S. brunae and S. massorum

Abstract New collections of Spinomantis frogs (Amphibia: Mantellidae: Mantellinae) have been made by us in northern Madagascar, and based on these collections we here describe two new species. One species, from northeastern Madagascar, has reduced dermal spines on the limbs and resembles S. massorum, but is diagnosed based on features including its shorter snout, proportionally longer hind limbs, reduced foot webbing, and different coloration. The other species, from the Tsaratanana Massif, is most similar to S. peraccae, but can be diagnosed based on features including its much larger body size, more extensive foot webbing and different coloration. We also redescribe two other poorly known species of Spinomantis: S. brunae and S. massorum. Both these rare species had been recently described based on a single and pair of type specimens respectively, and we here report on the morphology of new comparative material. For both the new and redescribed species, we summarize information on behavior, habits, indi...

A NEW SPECIES OF CHIASMOCLEIS MÉHELŸ, 1904 (ANURA, MICROHYLIDAE) FROM THE ATLANTIC RAINFOREST OF BAHIA, BRAZIL

We describe a new species of Chiasmocleis from the municipality of Una, in the Atlantic Rainforest of southern Bahia, northeastern Brazil. The new species is the smallest member of the genus and is characterized by having an ovoid body; a truncate snout in dorsal view, rounded snout in profile; no webbing on hands and feet; fingers lacking disks, toe tips slightly expanded; fingers and toes weakly fringed (less fringed in females), with few lateral dermal spines in males and none in females; the dorsal surface of body and limbs with dermal spines in males, absent in females; in preservative, color on dorsum uniformly grayish brown, paler brown on dorsal surface of limbs; posterior surface of thighs with a white, longitudinal line; and belly boldly marbled in brown and pale cream.