Diversification of the Neoselachii (Chondrichthyes) during the Jurassic and Cretaceous

The Neoselachii are a monophyletic group including all of the extant sharks and rays. They underwent rapid diversification throughout the Jurassic and Cretaceous, going from low-diversity assemblages of members of extinct orders in the Late Triassic to diverse assemblages containing representatives of most extant clades by the end of the Cretaceous. The known fossil record of Mesozoic neoselachians is composed largely of isolated teeth, with articulated skeletal remains being known from a limited number of sites. The small tooth size of a large proportion of neoselachians, including almost all taxa in existence prior to the mid Cretaceous, led to very poor representation in older publications. Their state of knowledge has improved dramatically since 1970 with the increased use of bulk sampling for isolated dental remains. Despite this, the high proportion of Lazarus taxa from some stages suggests that the state of knowledge is still intermittent. Increase in assemblage diversity throughout the Jurassic and Cretaceous suggests that radiation events resulted in real and dramatic increases in diversity, and that the perceived diversification is not an artefact of poor knowledge. Cladogenesis inferred from the fossil record typically compares more favourably with divergence predicted from molecular analysis, where Batoidea form a discrete basal clade, than with divergence predicted from morphological analysis, where Batoidea are considered a derived crown group within the Squalea. The timing of diversification events is discussed in light of the known fossil record, cladistically generated divergence times, and the paleoenvironmental distribution of faunas

Sequence variation among populations of sawfish (Pristiformes: Pristidae) from Indonesia and Australia

The sawfishes (Pristiformes: Pristidae) are very rare and critically endangered species globally, calling for conservation efforts around the world. This species is taxonomically interesting because molecular research in recent years has led to re-groupings in some species. The aim of this research was to sequence the control region (CR) of mitochondrial DNA of sawfishes from Indonesia and Australia, compare the sequences between samples, and construct phylogenetic trees to know the relationship of those samples. To achieve these aims, dried rostra of samples from both countries are collected, total DNA were purified and amplified using PCR, followed by sequencing reaction. The sequence data were then lined followed by constructing phylogenetic trees. The results of the BLASTN and phylogenetic tree analysis found two species, the all Australian samples belong to Pristis pristis (formerly P. microdon), one Indonesian sample also belongs to P. pristis, while the other Indonesian samples belong to Anoxypristis cuspidata

Species diversity of critically endangered pristid sawfishes (Elasmobranchii: Pristidae) of Nusantara waters (Malay Archipelago)

Sutarno, Setyawan AD, Suyatna I. 2012. Species diversity of critically endangered pristid sawfishes (Elasmobranchii: Pristidae) of Nusantara waters (Malay Archipelago). Biodiversitas 13: 161-171. The pristid sawfishes (Pristidae) are notable because of their saw- like rostrum and large body size (up to seven meters). All pristids are listed as critically endangered by IUCN, since decreasing population; Nusantara is home for five pristid species, namely: Anoxypristis cuspidata Latham, 1794, Pristis clavata Garman, 1906, Pristis microdon Latham, 1794, Pristis zijsron Bleeker, 1851, and Pristis pectinata Latham, 1794. A. cuspidata differ from Pristid spp. by the presence of a very narrow rostral saw, with 16 to 29 pairs of teeth except for the part along the quarter of the rostral saw near the head. P. microdon has a highly defined groove that runs along the entire posterior edge of the tooth into and beyond its confluence with the rostrum. This groove is absent in juvenile of P. clavata and whilst it develops in larger individuals it rarely runs along the entire posterior edge of the tooth or reach its confluence with the rostrum. P. clavata possibly have been misidentified as P. pectinata, whose distribution in the Indo-West Pacific is uncertain. P. clavata can be distinguished from P. pectinata and P. zijsron by the possession of fewer rostral teeth (18 to 22 in P. clavata cf. 24 to 28 in P. zijsron and 24 to 34 in P. pectinata), and by its smaller body size (i.e. less than 250 cm TL in P. clavata). P. microdon indicates different sexes of the number of rostral teeth, i.e. 17-21 in female cf. 19-23 in male, but in P. clavata, it can not be used to differentiate male from female, with both sexes possessing an average of 42 rostral teeth. In P. clavata the dorsal fin origin is opposite or slightly behind the pelvic fin origin, the rostum is relatively shorter (22-24% of TL), the lower cauda fin lobe is smaller

A Neoselachian shark from the non-marine Wessex Formation (Wealden Group: early Cretaceous, Barremian) of the Isle of Wight, southern England

Bulk screening of Early Cretaceous (Barremian) Wessex Formation strata exposed on the south-east coast of the Isle of Wight, southern England, has resulted in the recovery of neoselachian shark teeth referred to the scyliorhinid Palaeoscyllium. These are the first neoselachian remains from the British Wealden Group and represent the geologically oldest neoselachian yet recovered from a freshwater deposit. This is also the only known example of a non-marine occurrence of a member of the Scyliorhinidae

Distribución geográfica y estado de conservación de los peces sierra Pristis spp (Pristiformes: Pristidae) en el Caribe sur

The former presence of sawfishes (Pristis spp) is confirmed for the southern Caribbean Sea from the coasts of Colombia and Venezuela, based on review of eleven rostral saws exhibited in businesses, museums and private collections, as well as bibliographic references, photographs and surveys to detect sightings or captures in both countries. We determined that Pristis pristis and Pristis pectinata were present in the southern Caribbean coasts of Colombia and Venezuela, but that they are now probably locally extinct.Se confirma la presencia en el pasado de las especies de pez sierra (Pristis spp) en el mar Caribe de Colombia y Venezuela, a partir de la revisión de once extensiones rostrales exhibidas en establecimientos, museos y colecciones de particulares, así como la consulta bibliográfica, encuestas y el examen de material fotográfico disponible sobre avistamientos o capturas realizadas en ambos países. Se determinó que las especies presentes en el Caribe de Colombia y Venezuela eran Pristis pristis y Pristis pectinata, las cuales en la actualidad se encuentran probablemente extintas localmente

A rhinopristiform sawfish (Genus pristis) from the middle eocene (lutetian) of southern Peru and its regional implications

Modern sawfishes (Rhinopristiformes: Pristidae) are circumglobally distributed in warm waters and are common in proximal marine and even freshwater habitats. The fossil record of modern pristid genera (i.e., Pristis and Anoxypristis) dates back to the early Eocene and is mostly represented by isolated rostral spines and oral teeth, with phosphatised rostra representing exceptional occurrences. Here, we report on a partial pristid rostrum, exhibiting several articulated rostral spines, from middle Eocene strata of the Paracas Formation (Yumaque Member) exposed in the southern Peruvian East Pisco Basin. This finely preserved specimen shows anatomical structures that are unlikely to leave a fossil record, e.g., the paracentral grooves that extend along the ventral surface of the rostrum. Based on the morphology of the rostral spines, this fossil sawfish is here identified as belonging to Pristis. To our knowledge, this discovery represents the geologically oldest known occurrence of Pristidae from the Pacific Coast of South America. Although the fossil record of pristids from the East Pisco Basin spans from the middle Eocene to the late Miocene, sawfishes are no longer present in the modern cool, upwelling-influenced coastal waters of southern Peru. Given the ecological preferences of the extant members of Pristis, the occurrence of this genus in the Paracas deposits suggests that middle Eocene nearshore waters in southern Peru were warmer than today. The eventual disappearance of pristids from the coastal waters off southern Peru might be interpreted as reflecting the late Cenozoic trend of strengthening of the Humboldt Current

A new species of Dermopristis Kearn, Whittington & Evans-Gowing, 2010 (Monogenea: Microbothriidae), with observations on associations between the gut diverticula and reproductive system and on the presence of denticles in the nasal fossae of the host Glaucostegus typus (Bennett) (Elasmobranchii: Rhinobatidae)

Dermopristis cairae n. sp. (Microbothriidae) is described from the skin and possibly from the nasal fossae of the giant shovelnosed ray Glaucostegus typus (Bennett). The new species is distinguished from D. paradoxus Kearn, Whittington & Evans-Gowing, 2010 by its larger size, body shape, lack of transverse ridges on the ventral surface and absence of a seminal receptacle. Extensive short gut branches lie dorsal to the testes and adjacent to the coiled region of the vas deferens and the oo¨type, possibly reflecting high metabolic demand in these areas. Denticles are present in the lining of the nasal fossae of G. typus, providing a firm substrate for the cement-based attachment of a microbothriid. However, confirmation that D. cairae inhabits the nasal fossae of G. typus is required

Life history of the Critically Endangered largetooth sawfish: a compilation of data for population assessment and demographic modelling

© The authors 2021. Open Access under Creative Commons by Attribution Licence. Use, distribution and reproduction are un - restricted. Authors and original publication must be credited. The largetooth sawfish Pristis pristis is a Critically Endangered, once widespread shark-like ray. The species is now extinct or severely depleted in many former parts of its range and is protected in some other range states where populations persist. The likelihood of collecting substantial new biological information is now low. Here, we review all available life history information on size, age and growth, reproductive biology, and demography as a resource for population assessment and demographic modelling. We also revisit a subset of historical data from the 1970s to examine the maternal size−litter size relationship. All available information on life history is derived from the Indo-West Pacific (i.e. northern Australia) and the Western Atlantic (i.e. Lake Nicaragua-Río San Juan system in Central America) subpopulations. P. pristis reaches a maximum size of at least 705 cm total length (TL), size-at-birth is 72−90 cm TL, female size-at-maturity is reached by 300 cm TL, male size-at-maturity is 280−300 cm TL, age-at-maturity is 8−10 yr, longevity is 30−36 yr, litter size range is 1−20 (mean of 7.3 in Lake Nicaragua), and reproductive periodicity is suspected to be biennial in Lake Nicaragua (Western Atlantic) but annual in Australia (Indo-West Pacific). There was a weak relationship between litter size and maternal size in Lake Nicaragua, and lifetime reproductive output for an individual female from Lake Nicaragua was estimated as 73 pups. Future demographic models should aim to capture the variability and uncertainty in life history parameters for P. pristis and we encourage a conservative approach to any application for conservation and management

Evolutionary origins and development of saw-teeth on the sawfish and sawshark rostrum (Elasmobranchii; Chondrichthyes)

A well-known characteristic of chondrichthyans (e.g. sharks, rays) is their covering of external skin denticles (placoid scales), but less well understood is the wide morphological diversity that these skin denticles can show. Some of the more unusual of these are the tooth-like structures associated with the elongate cartilaginous rostrum ‘saw’ in three chondrichthyan groups: Pristiophoridae (sawsharks; Selachii), Pristidae (sawfish; Batoidea) and the fossil Sclerorhynchoidea (Batoidea). Comparative topographic and developmental studies of the ‘saw-teeth’ were undertaken in adults and embryos of these groups, by means of three-dimensional-rendered volumes from X-ray computed tomography. This provided data on development and relative arrangement in embryos, with regenerative replacement in adults. Saw-teeth are morphologically similar on the rostra of the Pristiophoridae and the Sclerorhynchoidea, with the same replacement modes, despite the lack of a close phylogenetic relationship. In both, tooth-like structures develop under the skin of the embryos, aligned with the rostrum surface, before rotating into lateral position and then attaching through a pedicel to the rostrum cartilage. As well, saw-teeth are replaced and added to as space becomes available. By contrast, saw-teeth in Pristidae insert into sockets in the rostrum cartilage, growing continuously and are not replaced. Despite superficial similarity to oral tooth developmental organization, saw-tooth spatial initiation arrangement is associated with rostrum growth. Replacement is space-dependent and more comparable to that of dermal skin denticles. We suggest these saw-teeth represent modified dermal denticles and lack the ‘many-for-one’ replacement characteristic of elasmobranch oral dentitions