Unique Synapomorphies Research Articles

An updated infrageneric classification based on phylogenomics and character evolution in Hydrangea (Hydrangeaceae)

AbstractThe genus Hydrangea s.l. (Hydrangeaceae), a favorite among gardeners, comprises more than 80 species that are important understory plants in natural temperate and subtropical forests of the Northern Hemisphere. These species are hypervariable in morphology, especially in indumentum and floral characters, warranting a thorough exploration of the complex evolutionary history of morphological characters of the genus. Ideally, this is done within a robust phylogenetic framework with extensive taxon sampling. In this study, we propose a comprehensive taxonomic reassessment of Hydrangea based on a reconstruction of its molecular phylogeny based mainly on the chloroplast genome (plastome) and the most representative taxon sampling reported to date. Phylogenomic reconstruction yielded five well‐resolved major clades and three newly recognized subclades. Inspection of the 28 characters employed in traditional taxonomic revisions revealed homoplasy in many of these traits. Our results show that characters such as growth habit, woody stem type, number of enlarged marginal sepals, style and stamen number, fruit shape, and ovary position are useful for circumscribing infrageneric divisions. Unique synapomorphies are limited. For example, herb and subshrub growth habits are associated with all the species in H. sect. Deinanthe and sect. Cardiandra, respectively. Character state combinations are proposed for distinguishing infrageneric taxa. Based on a robust phylogenetic framework, our findings suggest a complex evolutionary history of Hydrangea morphological characters. Following the criterion of monophyly and considering the morphological consistency and synapomorphy of single and combined characters to diagnose relevant lineages, we update the classification of Hydrangea into 5 subgenera and 19 sections. Our proposed taxonomic scheme, based on a robust phylogenetic framework and in‐depth character study, provides an updated perspective on the infrageneric subdivision of Hydrangea s.l.

Cuttlefishes (Cephalopoda, Sepiidae): the bare bones—an hypothesis of relationships

Based on a comprehensive analysis of molecular sequence data, the Sepiidae genera Acanthosepion Rochebrune, 1884; Ascarosepion Rochebrune, 1884; Aurosepina Jothinayagam, 1987; Decorisepia Iredale, 1926; Doratosepion Rochebrune, 1884; Rhombosepion Rochebrune, 1884 and Spathidosepion Rochebrune, 1884 are here re-instated and formally recognised as valid. Sepia Linnaeus, 1758 and Sepiella Gray, 1849 are retained, but Metasepia Hoyle, 1885 is placed in alternative combination with Ascarosepion. The subgenus Digitosepia Lipiński, 2020 is well supported and is herein elevated to generic status. Sepia trygonina (Rochebrune, 1884) and Sepia hieronis (Robson, 1924) are placed in new monotypic genera Erythalassa gen. nov. and Lusepia gen. nov. respectively. Hemisepius Steenstrup, 1875, also monotypic, is recognised as valid based on a unique synapomorphy: the presence of a fleshy ridge on each side of the antero-ventral mantle that bears a longitudinal row of black pores, however, H. typicus Steenstrup, 1875, was not included in our molecular analysis as tissue samples could not be obtained. Sepia tuberculata Lamarck, 1798, the type species for the nominal genus Spathidosepion, was not included for the same reason. Based on the morphological similarity between S. tuberculata and the sequenced taxa, S. papillata Quoy & Gaimard, 1832 and S. angulata Roeleveld, 1972 we tentatively assign these two taxa to Spathidosepion pending future confirmation. Where possible, each genus is diagnosed based on a combination of morphological and molecular characters.

A new species of the rare monotypic genus Cyrtinoclerus Chapin from Borneo, with notes on Meprinogenus Kolibáč (Coleoptera: Thanerocleridae).

Cyrtinoclerus sabahensis sp. nov. of the less diverse cleroid family Thanerocleridae is described from Borneo. The unique specimen was found in the Malaysian state of Sabah and represents the first collecting record of the genus in one hundred years. The new species is assigned to the hitherto monotypic genus Cyrtinoclerus Chapin, 1924, whose single species is known from a single specimen from Basilan, Philippines, with no subsequently collected specimens known to date. Cyrtinoclerus is distinct in its unique synapomorphies, namely the tarsi with formula 5-5-5 but tarsomeres 4 reduced in size, elytron depressed in basal third with distinct bulge, and seriate punctation of elytra. The genus is re-examined and again classified within Thanerocleridae. A systematic status of Cyrtinoclerus and its relative Meprinogenus Kolibáč, 1992, also known only from two just one-hundred-year-old specimens, is discussed and possible synonymy of the latter genus suggested. The family Thanerocleridae now comprises 38 extant species in eleven genera and four extinct Cretaceous genera and species found in Burmese and Charentese ambers. A phylogenetic analysis of all fifteen extinct and extant genera of Thanerocleridae based on 36 morphological characters is presented and updated key to the tribe Thaneroclerini provided.

Phylogenetic relationships of the Geoplaninae land planarians (Platyhelminthes, Tricladida) assessed with a total evidence approach, with the description of a new species of Gigantea

Several studies have focused on the phylogenetic relationships within the Geoplaninae land planarians (Tricladida). In those studies, ancient phylogenetic relationships remained obscure. In this work, the phylogeny of Geoplaninae is assessed through three different datasets, namely morphological, molecular, and both datasets combined, i.e, a total evidence approach (TE). The data matrix consisted of six DNA regions, including a newly developed marker (DOM5), and a morphological matrix with 37 characters. The study produced the best-resolved hypothesis so far for the phylogeny of Geoplaninae, although ancient clades still remain elusive. The effect of the morphological data on the TE tree topology and clade support is seemingly negligible. The phylogenetic tree also suggests that most of the diagnostic morphological characters of the genera are homoplastic, while unambiguous unique synapomorphies can characterize some supra-generic informal groupings.

Unique synapomorphies and high diversity in South American Raji-related Epstein-Barr virus genomes

Unique synapomorphies and high diversity in South American Raji-related Epstein-Barr virus genomes

Revision of Prodontocharax and revalidation of Amblystilbe (Teleostei: Characidae: Cheirodontinae), with description of a new species

Abstract Prodontocharax species are revised and the genus Amblystilbe is revalidated based on analysis of type-material and additional specimens. Both genera are diagnosed based on unique synapomorphies among members of the Cheirodontinae related to shape, size, number and arrangement of teeth in the jaw bones. Prodontocharax melanotus, from the upper rio Madeira basin, Brazil and Bolivia, is redescribed, and a new species is described from the rio Huallaga basin, Peru. The genus Amblystilbe and its type-species, A. howesi, are redescribed from the Amazonas River basin, Bolivia, Brazil, and Peru, and Prodontocharax alleni is considered a junior synonym of A. howesi. The two species of Prodontocharax are distinguished by the color pattern, number of lamellae of the olfactory rosette in male and female and number of gill rakers, and differ from A. howesi by the number and shape of teeth, color pattern and number of branched anal-fin rays. According to recent studies, the species of Prodontocharax and A. howesi cluster into two distinct clades among the cheirodontines.

Three new genera of Schizogyniidae (Parasitiformes: Mesostigmata) from a New Caledonian millipede (Spirobolida)

Three new monotypic genera of Schizogyniidae, Terrogynium gen. nov., Xenogynium gen. nov. and Zygogynium gen. nov., are described from a spirobolid millipede in New Caledonia. Terrogynium has females with chelicerae presumably modified for parasitism, and both sexes have numerous flattened ventral setae, convergent with many Paramegistidae. Xenogynium and Zygogynium are less-specialised genera with the former appearing closer to Terrogynium. Genus relationships are difficult to determine. These three genera are probably most closely related to each other but as a group it lacks convincing unique synapomorphies. Possible synapomorphies may instead reflect convergence for living on hosts, such as their shortened peritremes and loss of pretarsal claws, characters found elsewhere in the Schizogyniidae. The origins of the Schizogyniidae are discussed and a key to genera of Schizogyniidae is provided.

Morphological diversity and molecular phylogeny of five Paramecium bursaria (Alveolata, Ciliophora, Oligohymenophorea) syngens and the identification of their green algal endosymbionts

Paramecium bursaria is a mixotrophic ciliate species, which is common in stagnant and slow-flowing, nutrient-rich waters. It is usually found living in symbiosis with zoochlorellae (green algae) of the genera Chlorella or Micractinium. We investigated P. bursaria isolates from around the world, some of which have already been extensively studied in various laboratories, but whose morphological and genetic identity has not yet been completely clarified. Phylogenetic analyses of the SSU and ITS rDNA sequences revealed five highly supported lineages, which corresponded to the syngen and most likely to the biological species assignment. These syngens R1–R5 could also be distinguished by unique synapomorphies in the secondary structures of the SSU and the ITS. Considering these synapomorphies, we could clearly assign the existing GenBank entries of P. bursaria to specific syngens. In addition, we discovered synapomorphies at amino acids of the COI gene for the identification of the syngens. Using the metadata of these entries, most syngens showed a worldwide distribution, however, the syngens R1 and R5 were only found in Europe. From morphology, the syngens did not show any significant deviations. The investigated strains had either Chlorella variabilis, Chlorella vulgaris or Micractinium conductrix as endosymbionts.

Carinicateres merkli gen. et sp. nov. from Thailand, with notes on identification of two lophocateride beetles used in recent molecular phylogenies (Cleroidea, Lophocateridae)

Carinicateres merkli gen. et sp. nov. of Lophocateridae from eastern Thailand is described. The monotypic genus is distinct in its unique synapomorphies, namely the tarsal formula 4-4-4, elytron with 2 complete and 3 incomplete carinae, antenna 10-segmented with 2-segmented club. The emarginate frontoclypeal suture, mandible with mola, prementum divided into two parts, cranium dorsally with large impressions, each with seta in centre, crenulate lateral margins of pronotum, and distinct dorsal vestiture are shared with lophocateride genera Indopeltis Crowson and Trichocateres Kolibáč. Two specimens affiliated to Lophocateres Olliff and recently used in three molecular phylogenetic analyses are unambiguously identified as members of the clade Ancyrona + Neaspis and associated with Neaspis Pascoe.

Morphological phylogeny and review of the generic classification of Colletinae (Hymenoptera: Colletidae)

AbstractThe bee subfamily Colletinae includes 542 species, the vast majority of which (518 spp.) belong to Colletes. The generic placement of the remaining 24 species has been controversial, resulting in several classifications being proposed. Despite several recently published molecular phylogenies of Colletinae, it remains unknown (1) what morphological synapomorphies support the recognized genera, (2) in which direction some relevant functional traits (e.g. basitibial plate) have evolved and (3) whether morphology supports the available molecular data. Herein, we provide a morphological phylogeny of Colletinae, which was constructed through parsimony analyses of 186 characters. In total, 50 ingroup species were included representing all major lineages of Colletes (29 spp.), plus all but three of the non-Colletes species of Colletinae (21 spp.). Trees were estimated through equal weights and extended implied weighting. Both provide strong support for the monophyly of Colletinae and indicate that the subfamily is defined by four unique synapomorphies. Our results also confirm recent phylogenetic hypotheses showing that Colletinae can be subdivided into two major clades: one comprising the reciprocally monophyletic Mourecotelles and Xanthocotelles; the other includes Colletes plus Hemicotelles, which are also reciprocally monophyletic. We also provide a fully illustrated key to facilitate generic identification of the Colletinae.

Evolution of reproductive traits in the mahagony family (Meliaceae)

AbstractMeliaceae are a mostly pantropical family in the Sapindales, bearing flowers typically provided with a staminal tube, formed by filaments that are fused partially or totally. Nevertheless, several genera of subfamily Cedreloideae have free stamens, which may be adnate to an androgynophore in some taxa. The fact that the family exhibits a wide diversity of floral and fruit features, as well as of sexual systems and pollination syndromes, presents interesting questions on the evolutionary processes that might have taken place during its history. In this study, we analyzed the distribution of 20 reproductive morphological traits of Meliaceae, upon an available molecular phylogenetic framework, using 31 terminals from the family's two main clades (Cedreloideae and Melioideae), plus six Simaroubaceae taxa as outgroup. We aimed to identify and/or confirm synapomorphies for clades within the family and to develop hypotheses on floral evolution and sexual systems in the group. Our reconstruction suggests that the ancestor of Meliaceae was possibly provided with united stamens and unisexual flowers in dioecious individuals, with a subsequent change to free stamens and monoecy in the ancestor of Cedreloideae. Most characters studied show some degree of homoplasy, but some are unique synapomorphies of clades, such as the haplostemonous androecium. An androgynophore defines the Cedrela‐Toona clade. The comparative approach of our study and the evolutionary hypotheses generated herein reveal several aspects demanding further structural investigation, and possible evolutionary pathways of the reproductive structures along with the lineages' diversification, mostly related to the specialization of sexual systems, floral biology, and dispersal strategies.

A new species of Laccobius Erichson, 1837 (Hydrophilidae, Coleoptera) from the Chinese Himalaya, with comments on taxonomic status of subgenera Glyptolaccobius Gentili, 1989 and Cyclolaccobius Gentili, 1991 and additional faunistic records from China.

A new species of the water scavenger beetle, Laccobius (Glyptolaccobius) motuoensissp. nov., is described from Motuo County, Xizang, China and its diagnostic characters are illustrated. Examination of this new species and re-examination of previously described species revealed that the separation of the subgenus Glyptolaccobius Gentili, 1989 and Cyclolaccobius Gentili, 1991 is artificial: both subgenera are hence combined here. Cyclolaccobiussyn. nov. is synonymized with Glyptolaccobius, and the latter is shown to be diagnosed by 7-segmented antennae as a unique synapomorphy. All species treated until now under Cyclolaccobius are here transferred to Glyptolaccobius, with the only exception of L. hingstoni Orchymont, 1926, L. jumlanus Gentili, 2015 and L. zugmayeri Knisch, 1910 which are tentatively transferred to the subgenus Hydroxenus Wollaston, 1867, as their antennae bear eight antennomeres. Three species are recorded for the first time from China: L. (Microlaccobius) orientalis Knisch, 1924 from Xizang, Laccobius (M.) exilis Gentili,1974 from Xinjiang, and Laccobius (M.) sublaevis J. Sahlberg, 1900 from Xinjiang. Additional faunistic data from China are provided for the following species: L. (Microlaccobius) hammondi Gentili, 1984, Laccobius (M.) formosus Gentili, 1979, Laccobius (Hydroxenus) hingstoni d’Orchymont, 1926, Laccobius (Glyptolaccobius) yunnanensis Gentili, 2003, Laccobius (Compsolaccobius) decorus (Gyllenhal, 1827), Laccobius (Dimorpholaccobius) bipunctatus (Fabricius, 1775), Laccobius (D.) striatulus (Fabricius, 1775), Laccobius (s. str.) bedeli Sharp, 1884, L. (s. str.) binotatus d’Orchymont, 1934, Laccobius (s. str.) cinereus Motschulsky, 1860, and Laccobius (s. str.) minutus (Linnaeus, 1758).

Using Morphology to Test DNA-Based Phylogenetic Relationships within the Guiana Shield Catfish Tribe Lithoxini (Siluriformes: Loricariidae)

As DNA-based phylogenetic analyses have exploded, historically phenotype-based evolutionary hypotheses throughout the tree of life have been rewritten. However, rarely are DNA-based phylogenetic hypotheses tested via the reanalysis of phenotypic data. Skeletons representing all four recognized genera of the Guiana Shield endemic suckermouth armored catfish clade Lithoxini were examined to test a recently published DNA-based phylogenetic hypothesis using morphological evidence. Phylogenetic analysis of 54 mostly osteological characters yielded a single most parsimonious tree of 90 steps that was congruent with the molecular hypothesis: (Avalithoxus, ((Exastilithoxus), (Lithoxus, Paralithoxus))). Lithoxini was a well-supported clade with 20 synapomorphies, as was each of the genera within this clade. Avalithoxus jantjae, which was originally described in Lithoxus, was found to be missing the unique synapomorphies of Lithoxus Paralithoxus: a spoon-shaped, ventrally oriented process on the metapterygoid and a process on the preoperculo-hyomandibular ridge.

New damsel-dragonflies with “calopterygid”-like wing shape from the Middle Jurassic of China (Odonata: Isophlebioidea: Campterophlebiidae)

The new damsel-dragonflies Zygokaratawia incompleta nov. sp. and Parazygokaratawia azari nov. gen., nov. sp., closely related to the campterophlebiid genus Zygokaratawia, are described from the Middle Jurassic locality of the Daohugou and Chentaizi villages, respectively (Ningcheng County, Inner Mongolia, NE China). Parazygokaratawia nov. gen. and Zygokaratawia share a narrowly reduced cubito-anal area, unique synapomorphy in the Isophlebioptera. Campterophlebiids with this character are only known from the Daohugou biota.

Revision of the Bengalia torosa Wiedemann, 1819 species-group (Diptera: Calliphoridae), with notes on the systematic position of B. robertsi Kurahashi, 1987 and B. subnitida James, 1964.

The mainly Oriental Bengalia torosa Wiedemann species-group is revised on the basis of males. Species concepts are based on male terminalia. Monophyly of the species-group is established on the basis of two unique synapomorphies of the distiphallus. Eleven species are recognized as valid, viz. Bengalia chekiangensis Fan, 1965, Bengalia chiangmaiensis Kurahashi Tumrasvin, 1979, Bengalia concava Malloch, 1927, Bengalia escheri Bezzi, 1913, Bengalia fuscipennis Bezzi, 1913, Bengalia jejuna (Fabricius, 1787), Bengalia kanoi Kurahashi Magpayo, 2000, Bengalia martinleakei Senior-White, 1930, Bengalia recurva Malloch, 1927, Bengalia torosa (Wiedemann, 1819), Bengalia xanthopyga Senior-White, 1924, and their geographical distributions are updated. The following new synonymies are proposed: Bezzigalia rivanella Lehrer, 2005 is a junior synonym of B. escheri, syn. nov.; Bengalia siamensis Senior-White, 1924, Gangelomyia kosungana Lehrer, 2007 and G. laoziella Lehrer, 2007 are junior synonyms of B. fuscipennis, syn. nov.; Gangelomyia evafoneae Lehrer, 2005 and G. senausmarta Lehrer, 2005 are junior synonyms of B. jejuna, syn. nov.; Gangelomyia indipyga Lehrer, 2005, G. philipyga Lehrer, 2005, G. schiavoae Lehrer, 2005, G. shivanella Lehrer, 2005, G. tagaloga Lehrer, 2005 and G. phantastika Lehrer, 2007 are junior synonyms of B. kanoi, syn. nov.; Gangelomyia gandhiana Lehrer, 2005 and G. krishna Lehrer, 2005 are junior synonyms of B. martinleakei, syn. nov.; Laoziana camerina Lehrer, 2005, L. mandarina Lehrer, 2005 and L. singhasaria Lehrer, 2005 are junior synonyms of B. recurva, syn. nov. Lectotypes are designated for Musca favillacea Walker, 1859 and Bengalia escheri Bezzi, 1913. A male syntype of Musca torosa Wiedemann, 1819 has been located in NHMD and a female syntype of the same nominal species has been located in NMW. A male specimen in NHMD is proposed as neotype for Musca jejuna Fabricius, 1787, to replace the three existing female syntypes. A male specimen in NHMD is proposed as neotype for Musca torosa Wiedemann, 1819, to replace the newly located syntypes. The ICZN Commission will be requested, in a forthcoming paper, to formally set aside the existing name-bearing types of both nominal species and designate the proposed specimens as neotypes, in order to preserve the current usage of both names. Musca favillacea Walker, 1859 is removed from synonymy with Bengalia jejuna and treated as an unplaced name in the Bengalia torosa species-group. Bengalia robertsi Kurahashi, 1987 is removed from the Bengalia torosa species-group and re-assigned to the Bengalia labialis Robineau-Desvoidy species-group. Bengalia subnitida James, 1964 is assigned to the Bengalia peuhi Villeneuve species-group even though it lacks discal setae on the fifth abdominal tergite. Two new terms are introduced for description of the distiphallus of the B. torosa species-group. Bengalia recurva Malloch is reported for the first time from China.

Phylogeny and relationships of the neotropical Adiantum raddianum group (Pteridaceae)

AbstractWith more than 200 species, the maidenhair fern genus Adiantum is among the top ten most diverse fern genera. Adiantum is pantropical in distribution and, due to the presence of a unique synapomorphy (sporangia borne on indusia rather than laminae), perhaps the most easily recognized fern genus. Many of its members, including numerous cultivars derived from A. raddianum, are grown as ornamentals. Because of its size, a comprehensive taxonomic study of Adiantum is difficult and the genus is perhaps better approached through a series of narrower studies. Here, we focus specifically on A. raddianum and putative allies. We find a newly defined A. raddianum group to be strongly supported as monophyletic and segregated from other maidenhair ferns on the basis of genetic as well as morphological characteristics. Bayesian inference and maximum likelihood analyses of plastid atpA, chlL, chlN, rbcL, and rpoA sequences support the A. raddianum clade as sister to A. poiretii and its allies. We identify round‐reniform indusia to be a characteristic of the A. raddianum group (vs. lunate in the A. poiretii group). Additionally, we find species in the A. poiretii group to differ in having a unique 66 nucleotide deletion in our chlN gene alignment. The neotropical A. raddianum group comprises at least 17 species (14 studied here), some widely distributed; one was recently described (A. alan‐smithii).

Review of the western African millipede genus Diaphorodesmus Silvestri, 1896 (Diplopoda, Polydesmida, Chelodesmidae), with the description of a similar, but new monotypic genus from Cameroon.

The genus Diaphorodesmus is revised and shown to comprise only a single species, Diaphorodesmus dorsicornis (Porat, 1894) by priority, with the only other formal congener, Diaphorodesmus attemsii Verhoeff, 1938, considered as its junior subjective synonym, syn. n. A new monotypic genus, Diaphorodesmoides gen. n., is created to include Diaphorodesmoides lamottei sp. n., from southwestern Cameroon. Both these genera seem to be especially similar in sharing remarkable dorsal horns on metaterga 2–4, a unique synapomorphy in the basically Afrotropical subfamily Prepodesminae, family Chelodesmidae, to which they belong. In contrast to Diaphorodesmus which shows two, increasingly short, paramedian horns on each of metaterga 2–4, the ozopores borne on distinct porosteles, and the gonopod prefemoral process and solenophore less strongly elaborate, Diaphorodesmoides gen. n. has a single, increasingly large, central horn on each of metaterga 2–4, the ozopores opening flush dorsolaterally on the surface of poriferous paraterga, and both the gonopod prefemoral process and solenophore especially complex. The genus Campodesmoides VandenSpiegel, Golovatch & Nzoko Fiemapong, 2015, and its sole, and type, species Campodesmoides corniger VandenSpiegel, Golovatch & Nzoko Fiemapong, 2015, are transferred from Campodesmidae to Chelodesmidae and formally synonymized with Diaphorodesmus and Diaphorodesmus dorsicornis, both syn. n.

Taxonomy of 'Euconnus complex'. Part VII. Glabriconnus, a new subgenus of Euconnus from Madagascar (Coleoptera, Staphylinidae, Scydmaeninae).

A new subgenus of Euconnus Thomson is described, Glabriconnus subgen. n., to accommodate four Madagascan species: Euconnus banari sp. n. (type species of Glabriconnus), E. andranomenaus sp. n., E. februarius sp. n. and E. aterrimus Franz (transferred from Euconnus s. str.). Morphological structures of the new taxa are illustrated and described in detail, and possible relationships of Glabriconnus are discussed. The new subgenus is most similar to Tetramelus Motschulsky and Paratetramelus Franz in gradually thickened antennae and reduction of wings and associated structures, but the four species included in Glabriconnus share a unique synapomorphy, a hypomeral groove at each side of pronotum. They also have a broad, short and flattened 'anthiciform' head; nearly glabrous head, pronotum and elytra, except for thick bristles on genae, postgenae (but not tempora) and along anterior and lateral pronotal margins, and pronotum with one pair of distinct lateral pits.

Morphological Evidence for the Monophyly of the Subfamily of Parasitic Catfishes Stegophilinae (Siluriformes, Trichomycteridae) and Phylogenetic Diagnoses of Its Genera

The subfamily of Neotropical parasitic catfishes Stegophilinae (Trichomycteridae) is a remarkable group given its specialized feeding habits (lepidophagy, muciphagy, and necrophagy). Despite its biological interest, the systematics of this group has remained in an incipient state. Most genera lack a phylogenetic diagnosis, leading thus to taxonomic instability at that level. Similarly, the hypothesis of monophyly of Stegophilinae is supported by scant morphological evidence. In this study, based on a broad morphological comparative survey of representative genera and species of each subfamily of Trichomycteridae, new evidence is provided to support Stegophilinae as a monophyletic unit. Stegophilinae is herein recognized by four unique synapomorphies, three of them proposed here for the first time. Additionally, phylogenetic diagnoses are offered for all currently recognized genera (including Pareiodon), except Parastegophilus which is placed in the synonymy of Pseudostegophilus. An identification key for ...

Danionella dracula, an escape from the cypriniform Bauplan via developmental truncation?

We provide a detailed account of the osteology of the miniature Asian freshwater cyprinid fish Danionella dracula. The skeleton of D. dracula shows a high degree of developmental truncation when compared to most other cyprinids, including its close relative the zebrafish Danio rerio. Sixty-one bones, parts thereof or cartilages present in most other cyprinids are missing in D. dracula. This impressive organism-wide case of progenesis renders it one of the most developmentally truncated bony fishes or even vertebrates. Danionella dracula lacks six of the eight unique synapomorphies that define the order Cypriniformes and has, thus, departed from the cypriniform Bauplan more dramatically than any other member of this group. This escape from one of the most successful Baupläne among bony fishes may have been facilitated by the organism-wide progenesis encountered in D. dracula. By returning in its skeletal structure to the early developmental condition of other cypriniforms, D. dracula may have managed to overcome the evolutionary constraints associated with this Bauplan and opened up new evolutionary avenues that enabled it to evolve a number of striking morphological novelties, including its tooth-like odontoid processes and a complex drumming apparatus.