A longstanding entomological problem finally solved? Head morphology of Nannochorista (Mecoptera,Insecta) and possible phylogenetic implications

External and internal head structures of Nannochorista species were examined and described in detail. The characters are discussed with regard to their functional and phylogenetic implications. The structure of the mouthparts indicates that adults of Nannochorista feed on fluids. The loss of the mandibular muscles and the precerebral pharyngeal dilators are presumptive autapomorphies of the genus. A possible clade comprising Nannomecoptera, Siphonaptera and Diptera is supported by the presence of a labral food channel, the absence of the galea, a sheath for the paired mouthparts formed by the labium, very strongly developed labial palp muscles and cibarial dilators, and the presence of a well‐defined postcerebral pharyngeal pumping chamber. Closer affinities of Nannomecoptera with Diptera are suggested by the presence of a unique sensorial groove on the third maxillary palpomere. Further potential synapomorphies are the presence of a frontal apodeme and a primarily lamelliform mandible without teeth. The presence of a salivary channel on the laciniae and a subdivided labrum are shared derived features of Nannochorista and Siphonaptera. A derived condition present in Mecoptera including Boreidae but excluding Nannochoristidae is the secretion with a strongly developed intrinsic muscle of the salivary duct. The loss of the lateral labral retractor, the cranial muscle of the cardo, and of two of the three premental retractors, and the absence of transverse epipharyngeal muscles are potential autapomorphies of Antliophora. The formation of a maxillolabial complex is a possible synapomorphy of Hymenoptera and Mecopterida.     

Comments on the evolution of the jaw adductor musculature of snakes

The aim of this study is to provide a general view of the adductor musculature of the alethinophidian snakes. The aponeurotic system present in anilioid snakes is here described as being also present in colubroid and booid snakes. Although modified in various groups, this aponeurotic system retains the same topographical pattern in the anilioids, booids and colubroids, and is thus hypothesized to be homologous. An analysis of the aponeurotic system and related muscular bundles within the alethinophidian snakes is given. A new terminology is proposed for the jaw adductor muscles where the muscles levator anguli oris and adductor mandibulae externus superficialis (proper) of snakes (sensu Lakjer, 1926; Haas, 1962) retain these names even if this fails to reflect the presumed homologies with the bundles of the same name in lizards (see Rieppel, 1988b); the fibres originating from the temporal tendon in the Anilioidea, and presumed to form a bundle of composite nature (Rieppel, 1980b), are named the M. adductor mandibulae externus temporalis (lost by the Macrostomata); the M. adductor mandibulae externus medialis is a composite muscle in the Anilioidea (Rieppel, 1980b) which give rise to two different muscles in the ‘booids’, the M. adductor mandibulae externus medialis, pars anterior and the M. adductor mandibulae externus profundus, the former being secondarily lost by the Caenophidia which retains only fibres homologues of the 3b and 3c heads of the profundus layer of lizards; the so-called M. adductor mandibular externus profundus of snakes (sensu Lackjer, 1926; Haas, 1962) is also a composite muscle in the Anilioidea (Rieppel, 1980b), in the alethinophidians it is essentially made of fibres homologous with the posterior pinnate part of the medialis layer of lizards, and is here named the M. adductor mandibulae externus medialis, pars posterior. As a result from this analysis it follows that: (1) the Macrostomata are characterized by the downward extension of the fibres forming the M. adductor mandibulae externus medialis, pars anterior and the loss of the M. adductor mandibulae externus temporalis: (2) the Xenopeltidae are set apart from the remaining macrostomatan snakes by the retention of the M. levator anguli oris and of a well developed lateral sheet of the quadrate aponeurosis; (3) the ‘booids’ form a monophyletic group comprising only the Boidae and Bolyeriidae (with the exclusion of the Xenopeltidae and Tropidophiidae) which is characterized by a differentiated M. adductor mandibulae externus medialis, pars anterior inserting on the lateral surface of the compound bone via its own aponeurosis; (4) the Tropidophiidae are set apart from all other snakes by the peculiar course of their lateral head vein; however, they belong to the Caenophidia as they show a facial carotid artery which passes dorsally to the mandibular and maxillary branches of the trigeminus; (5) a possible additional character in favour of an Acrochordoidea + Colubroidea monophyletic unit may be given by the pattern of innervation of the jaw adductor muscles in these two taxa; (6) a new interpretation of the compressor glandulae muscular complex of Atractaspis resulted in a morphologically similar pattern to that of the viperids; the phylogenetic implications of such similarity are discussed in detail.     

Resolving insect phylogeny: The significance of cephalic structures of the Nannomecoptera in understanding endopterygote relationships

The Nannomecoptera are among the most enigmatic and controversial taxa of endopterygote insects, the phylogenetic resolution of which is crucial to understanding the evolution of neopteran insects. Once considered a subordinate lineage within the Mecoptera, renewed interest in nannochoristids has been prompted by evidence that the Nannomecoptera are not admissible to the clade of extant scorpion flies but are more likely to belong to the clade Siphonaptera + Nannomecoptera + Diptera. The overarching purpose of the present account is to provide novel and extensive morphological character traits in addition to those already existing for adult structures. The aim is to determine if these traits support molecular data sets that have been suggested elsewhere to clarify the phyletic position of Nannochoristidae. This account focuses on nannomecopteran larvae, which unlike those of other mecopterans have received little attention. Thus, the thrust of this investigation is to provide detailed anatomical data on nannochoristid larvae for a targeted inquiry into their phylogenetic affinities. The described characters are discussed and presented in a data matrix comprising representatives of all endopterygote orders. While the study is based primarily on the New Zealand species Nannochorista philpotti, it is proposed that all nannomecopteran larvae will prove to be similar to this taxon in most if not all structural features of significance to a higher-level phylogenetic context.     

The female postabdomen of the enigmatic Nannochoristidae (Insecta: Mecopterida) and its phylogenetic significance

Hünefeld, F. and Beutel, R.G. 2011. The female postabdomen of the enigmatic Nannochoristidae (Insecta: Mecopterida) and its phylogenetic significance. —Acta Zoologica (Stockholm) 00: 1–8. External and internal features of the female postabdomen of Nannochorista neotropica are described in detail. The conditions found in females of Nannochoristidae come closest to the ground plan of Mecopterida. This lineage is characterised by telescoping postabdominal segments, a presumptive autapomorphic feature that is modified in some antliophoran groups, but displayed by the nannochoristid species in a typical manner. More potential autapomorphies of Mecopterida, all present in Nannochoristidae, are the neo‐formation of an intersegmental muscle, a transverse muscle spanning between the genital appendages of segment VIII, a muscle connecting these appendages and the genital chamber and the loss of an intersegmental muscle. Plesiomorphic features of Nannochoristidae are the presence of paired genital appendages on segments VIII and IX. Information on the egg‐depositing substrates of the females is not available. The telescoping postabdomen is suitable for oviposition in soft substrates such as moist soil, or rotten plant materials in the riparian zone, and this is possibly a ground‐plan feature of Mecopterida. The results of recent phylogenetic analyses based on morphological data support a placement of Nannochoristidae in Antliophora, whereas the exact position of the group remains ambiguous. No characters of the female postabdomen were found supporting the monophyly of Mecoptera as conventionally circumscribed, that is Nannochoristidae + Boreidae + Pistillifera.