Independent Acquisition of Carnassial Teeth in Fishes and Mammals

Vertebrates evolved tooth replacement over 400 million years ago. Over 200 million years later, the combination of vertical tooth replacement with thecodont implantation (teeth in bone sockets) has been considered a key morphological innovation in mammal evolution. We discovered that an extinct fish taxon, Serrasalmimus secans, that shows this same innovation in a lineage (Serrasalmimidae) that survived the end Cretaceous mass extinction. Carnassial teeth are known in both mammals and pycnodont fish, but these teeth do not share the same tissues nor developmental processes. Therefore, a serrasalmimid pycnodont fish independently acquired mammal-like tooth replacement and implantation, thus showing that fishes and mammals evolved convergent carnassial dental morphologies at about the same time, around 60 Ma, in separate ecosystems.

The oldest species of Peltoperleidus (Louwoichthyiformes, Neopterygii) from the Middle Triassic (Anisian) of China, with phylogenetic and biogeographic implications

The previously alleged ‘perleidid’ genus Peltoperleidus is a stem-neopterygian fish taxon with two or three horizontal rows of notably deepened flank scales. Until recently, members of this genus were known only from the Ladinian (late Middle Triassic) or near the Anisian/Ladinian boundary (~242 Ma) in southern Switzerland and northern Italy. Here, I report the discovery of a new species of the genus, Peltoperleidus asiaticus sp. nov., based on three well-preserved specimens from the Anisian (early Middle Triassic, ~244 Ma) of Luoping, eastern Yunnan, China. The discovery extends the geological range of Peltoperleidus by approximately two million years and documents the first record of the genus in Asia. Similar to its relatives (represented by P. macrodontus) from Europe, P. asiaticus sp. nov. is likely a small-sized durophagous predator with dentition combining grasping and crushing morphologies. Results of a cladistic analysis unite four species of Peltoperleidus as a monophyletic group within the Louwoichthyiformes, and suggest that the presence of two horizontal rows of notably deepened scales was independently evolved in Peltoperleidus and another stem-neopterygian taxon Altisolepis. P. asiaticus sp. nov. is nested at the base of Peltoperleidus, and a new family Peltoperleididae is proposed for the genus, contrasting the previous placement of Peltoperleidus in the poorly defined, paraphyletic ‘Perleididae’. Comparative studies of the basal peltoperleidid from China with its younger relatives from Europe provide new insights into the evolutionary origin and paleogeographic distribution of this clade.

Updated Genome Assembly of Bighead Carp (Hypophthalmichthys nobilis) and Its Differences Between Male and Female on Genomic, Transcriptomic, and Methylation Level

Cyprinidae is one of the largest family in freshwater fishes, and it is most intensively cultured fish taxon of the world. However, studies about sex determination in this large family is still rear, and one of the reasons is lack of high quality and complete genome. Here, we used nanopore to sequence the genome of a male bighead carp, obtaining contig N50 = 24.25 Mb, which is one of the best assemblies in Cyprinidae. Five males and five females were re-sequenced, and a male-specific region on LG19 was confirmed. We find this region holds many male-specific markers in other Cyprinidae fishes, such as grass carp and silver carp. Transcriptome analyses of hypothalamus and pituitary tissues showed that several sex-specific differentially expressed genes were associated with steroid biosynthesis. The UCH64E gene, located in the male-specific region on LG19, showed higher expression levels in male than female tissues of bighead carp. The methyl-RAD of hypothalamus tissues between males and females indicated that the sexual methylation differences are significant in bighead carp. We also compared the methylation sites recognized using methyl-RAD and nanopore raw reads and found that approximately 73% of the methylation sites identified using methyl-RAD were within nanopore CpG sites.

Postcranial skeletal development of Mugil cephalus (Teleostei: Mugiliformes): morphological and life-history implications for Mugiliformes

Within the fish taxon Mugiliformes, the larval development of Mugil cephalus has been studied most intensively, because it has the widest range of distribution among all mugilids and is of interest to aquaculture all over the world. Although numerous studies have dealt with larval rearing, growth and development, the osteological development of M. cephalus and mugiliforms in general has largely been neglected. Herein, we describe the skeletal development of mullets for the first time. Cleared and double-stained specimens of aquaculture-reared M. cephalus and wild-caught mugilid larvae were examined to describe the early development of the pectoral and pelvic girdle, the vertebral column and the caudal and median fins. The description of four embryonic and six larval developmental steps within the embryonic and larval period enables us to compare larval sizes of reared and wild-caught larvae. Ontogenetic fusions of ural centra 1 and 2 into a compound centrum, in addition to the fusion of two pterygiophores in the anal fin, have implications for the perception of the adult morphology. Moreover, comparison of mugilid development with that of other ovalentarian taxa shows that recent phylogenetic hypotheses need further morphological investigation.

Osteology and phylogeny of Robustichthys luopingensis, the largest holostean fish in the Middle Triassic

The extinct ray-finned fish taxon Robustichthys luopingensis from Luoping, eastern Yunnan, China represents the largest holostean known in the Middle Triassic. Despite its potential significance for investigating the holostean phylogeny and reconstructing the Triassic marine ecosystems, Robustichthys has so far not been described in detail and its phylogenetic position within the Holostei was controversy. This study provides a redescription and revision of Robustichthys based upon a comparative study of eight type specimens and nine new specimens. Newly recognized information includes a toothed parasphenoid, a pair of premaxillae not pierced by the olfactory nerve, a splint-like quadratojugal, a hatchet-shaped hyomandibula, an hourglass-shaped symplectic, anterior and posterior ceratohyals, a complete series of branchiostegal rays, and sclerotic bones. A revised reconstruction of Robustichthys is presented. Results of a cladistic analysis confirmed Robustichthys as an ionoscopiform within the Halecomorphi; the previous placements of Robustichthys as a basal ginglymodian and Ionoscopidae as a basal amiiform clade are not supported. The sister group relationship between Sinamiinae (Sinamia and Ikechaoamia) and Amiinae (Amia and Cyclurus) within the Amiidae is newly recognized. This revised topology provides new insights into the evolution and historical paleoecology of halecomorph fishes.

High background risk induces risk allocation rather than generalized neophobia in the fathead minnow

To cope with the heterogeneous nature of predation and the trade-off between predator avoidance and foraging, prey animals have evolved several cognitive rules. One of these is the risk allocation hypothesis, which predicts that in environments with long periods of sustained high risk, individuals should decrease their antipredator effort to satisfy their metabolic requirements. The neophobia hypothesis, in turn, predicts increased avoidance of novel cues in high-risk habitats. Despite the recent interest in predator-induced neophobia across different sensory channels, tests of such generalized neophobia are restricted to a single fish taxon, the Cichlidae. Hence, we retested the generalized neophobia hypothesis in fathead minnows Pimephales promelas, a small schooling North American cyprinid fish. From hatching onward, minnows were exposed to conspecific alarm cues, which indicate predation risk, or distilled water in a split-clutch design. After 1 month, shoaling behavior was examined prior and subsequent to a mechanical predator disturbance. Fish previously exposed to elevated background risk formed compact shoals for a shorter time interval after the stimulus compared with controls. These results contrast previous studies of generalized neophobia but match the risk allocation hypothesis. Consequently, risk allocation and generalized neophobia are not ubiquitous cognitive rules but instead evolved adaptations of different taxa to their respective environments.

Correction Notice

Ewonus, P. A. (2017). Assessing internal household relationships and site use: Zooarchaeological evidence from Dionisio Point, Galiano Island, Canada. North American Archaeologist, 38(4), 349–393. DOI: 10.1177/0197693117727392 In this article, which was published in volume 38, issue 4 of North American Archaeologist, the following corrections have been identified by the author: Abstract, line 7: The word “consisted” should be “comprised”. Figure 2: The image file layer containing the four archaeological sites referenced in this figure has been moved to underlay the base map layer. The revised figure is provided below. Page 357, line 3: The closing parenthesis should appear after “8.0mm” in the following sentence: “Examination of their data (Grier et al., 2013: 548–550) reveals that approximately half of this difference between salmon vertebra size in their overall sample (38.1%≥8.0 mm) and successful aDNA species identification (62.7%≥8.0 mm) is due to sampling that may be non-random (of the 149 vertebrae sampled for aDNA analysis with transverse diameter values presented in Grier et al. (2013), 75 (50.3%)≥8.0 mm).” Headings appearing on pages 363, 366, and page 367 are tertiary (H3), not primary headings (H1). Page 369, final line: “Comprised” was erroneously changed to “consisted”. The correct sentence should be: “Six other units, comprised of two that contain a major hearth (144N/116E, 147N/124E), … mammal remains.” Table 2: The fish taxon row title “ Theragra chalcogramma” was moved to page 362 in the table, while the specific data for this entry remains as the final row of the table page 361. Table 3: “Carnivora”, “Cetacea”, “Rodentia”, and “Miscellaneous” should be bolded headings. Table 4: “Anseriformes” (at top) should be bolded. Table 5: “Echinoidea” (at top) should be bolded. Page 376: In the following final sentence “remain” should read “remains”: “Of the fish elements recovered, only those from an individual 5 cm level in 10 excavation units were used in the assessment of horizontal faunal distributions (NISP = 3294, NSP = 6945). Mammal (NISP = 1451) and bird (NISP = 646) remain from all levels associated with the House 1 occupation, recovered in 6.4mm screens from 12 units, were examined for horizontal patterns (Frederick, 2012).” Page 381: The heading “Departure bay” should be “Departure Bay”. Pages 381, 384: Headings “Departure Bay”, “Tsawwassen VI, VII, and VIII”, and “Site comparison” should be tertiary headings (H3). Page 387, line 7: An unnecessary comma was inserted following the word Research in this final line of the Acknowledgments section. Page 393, Author biography: Inserting “the” before “Cambridge University” and “Vancouver Island University” was in error.

New remarkable Late Jurassic teleosts from southern Germany: Ascalaboidae n. fam., its content, morphology, and phylogenetic relationships

Complete morphological descriptions, as preservation permits, are provided for a new Late Jurassic fish taxon (Ebertichthys ettlingensis n. gen. et n. sp.) and a revision of some morphological features of Ascalabos voithii Graf zu Münster from the Solnhofen limestones, southern Germany. A new family, Ascalaboidae, is erected to include the two species. The new family is supported by numerous synapomorphies, e.g., maxilla with external row of small conical teeth increasing in size posteriorly, absence of gular plate, low number of vertebrae (34 to 39), deep and narrow supracleithrum – deeper than opercle, and vertebral centrum formation of caudal region including paired chordacentra (pseudo-diplospondyly) that fuse in early ontogeny forming one chordacentrum that is later surrounded by an autocentrum. A phylogenetic analysis based on 173 characters and 42 taxa was performed. Following the phylogenetic hypothesis, the sister-group relationship [Ascalabos + Ebertichthys] + more advanced teleosts stands above the node of Leptolepis coryphaenoides plus more advanced teleosts and below the node of Tharsis plus more advanced teleosts, and the new taxa are interpreted as extinct and primitive forms within Teleostei. The new genus and species is endemic and restricted to one Upper Jurassic locality – Ettling – whereas Ascalabos is known from different localities in the Solnhofen limestones, with the exception of Ettling.

Freshwater actinopterygians of the Los Rastros Formation (Triassic), Bermejo Basin, Argentina

The present paper includes detailed descriptions of all fossil fishes known from the Los Rastros Formation (Ladinian; Bermejo Basin, Argentina). Four taxa are identified: Gualolepis carinaesquamosa n. gen. n. sp., Rastrolepis n. gen. with two species R . riojaensis n. sp. and R. latipinnata n. sp., and Challaiaelongata n. comb. Gualolepis n. gen. and Rastrolepis n. gen. are incertae sedis actinopterygians. The opercular bones of Gualolepis resemble those in peipiaosteid acipenseriforms and the fish might be related with the Chondrostei. The most distinctive features of Rastrolepis are the narrow opercular region and the presence of a very large plate-like branchiostegal bone resembling the condition in the Redfieldiiformes. Challaiaelongata, originally described in the Australian genus Myriolepis, is here refered to the genus Challaia, previously known from the nearby Cuyo Basin and representing the first fish taxon common to both continental sequences. Furthermore, Challaia is shown to be a member of the Acrolepidae and represents the youngest record of the family in Gondwana. Alle fossilen Fische, die bisher von der Los Rastros Formation (Ladin; Bermejo-Becken, Argentinien) bekannt sind, werden im Detail beschrieben. Vier Taxa können identifiziert werden: Gualolepis carinaesquamosa n. gen. n. sp., Rastrolepis n. gen., mit zwei Arten, R . riojaensis n. sp. und R . latipinnata n. sp., und Challaiaelongata comb. nov. Gualolepis n. gen. und Rastrolepis n. gen. Actynopterygier unsicherer systematischer Stellung. Die Operkular-Knochen von Gualolepis ähneln jenen der peipiaosteiden Acipenseriformen und das Taxon mag mit den Chondrostei verwandt sein. Die auffälligsten Merkmale von Rastrolepis sind die sehr schmale Operkularregion und das Vorhandensein eines sehr großen, plattigen Branchiostegale, das dem Zustand in Redfieldiiformen ähnelt. Challaiaelongata, ursprünglich zu der australischen Gattung Myriolepis gestellt, wird hier der Gattung Challaia zugeordnet, die bisher nur aus dem nahegelegenen Cuyo-Becken bekannt war und repräsentiert somit das erste Fisch-Taxon, das in beiden Sequenzen vorkommt. Zudem kann gezeigt werden, dass Challaia zu den Acrolepidae gehört und somit den jüngsten Nachweis dieser Gruppe in Gondwana darstellt. doi:10.1002/mmng.200600011