Velvet Photomorphs

The velvet ants of the family Mutillidae are a diverse but relatively little-studied group of insects. As well as their often retiring habits, studies of this family are hindered by the difficulty of associating sexes. Females are wingless and superficially resemble hairy ants. Males are usually winged and resemble more typical wasps (there is a small handful of species in which both sexes are flightless). What we do know of velvet ant diversity suggests a high level of endemicity with different regions each having their own distinct assemblages of genera and species. In North America, one of the most diverse recognised genera is Photomorphus.

Female Photomorphus banksi, copyright Cotinis.

Species of Photomorphus are found across much of the United States and Mexico, being most diverse in the arid regions of the south-west (Brabant et al. 2010). The genus is currently divided between three subgenera, each originally described from males. Males have round, slightly protruding eyes, a more or less petiolate metasoma with a distinct constriction between the first and second segments, and a pair of ridges on the mesosternum behind the procoxae. The genus is currently divided between three subgenera: Photomorphus, Photomorphina and Xenomorphus. Males of subgenus Photomorphus have a distinct space between the mesocoxae and bidentate mandibles whereas Photomorphina males have the mesocoxae closely placed and tridentate mandibles (Manley & Pitts 2002). Females of Photomorphus have dense, silver setae on the mesosoma whereas females of Photomorphina have a less hairy mesosoma and typically have a band of plumose setae along the dorsal hind margin of the second metasomal segment (Brabant et al. 2010). The third subgenus, Xenomorphus, is known from a single Mexican species only and its female remains unidentified.

Male Photomorphus paulus, copyright J. C. Jones.

Photomorphus is part of a lineage of nocturnal mutillids common in arid regions of North America. Velvet ants develop as nest parasites of other wasps and bees; Photomorphus species are presumably no exception but their hosts are as yet unknown. A phylogenetic analysis of the North American nocturnal mutillids by Pitts et al. (2010) supported recognition of the group as a single clade but identified Photomorphus itself as polyphyletic. A clade corresponding to the subgenus Photomorphus was recovered but Photomorphina species were divided between multiple separate clades. This included the species P. myrmicoides which Brabant et al. (2010) had suggested should be moved from Photomorphina to subgenus Photomorphus. Females of P. myrmicoides have hair like that of subgenus Photomorphus but differs in the structure of the pygidial plate, a hairless area at the end of the metasoma. In the strict subgenus Photomorphus, this plate is completely smooth and shiny; in Photomorphina and P. myrmicoides, it is rough or marked by ridges. Clearly a reclassification of Photomorphus is on the cards but we are yet to see when we have the confidence to enact it.

REFERENCES

Brabant, C. M., K. A. Williams & J. P. Pitts. 2010. True females of the subgenus Photomorphina Schuster (Hymenoptera: Mutillidae). Zootaxa 2559: 58–68.

Manley, D. G., & J. P. Pitts. 2002. A key to genera and subgenera of Mutillidae (Hymenoptera) in America north of Mexico with description of a new genus. Journal of Hymenoptera Research 11 (1): 72–100.

Pitts, J. P., J. S. Wilson & C. D. von Dohlen. 2010. Evolution of the nocturnal Nearctic Sphaerophthalminae velvet ants (Hymenoptera: Mutillidae) driven by Neogene orogeny and Pleistocene glaciation. Molecular Phylogenetics and Evolution 56: 134–145.

Lichen Darklings

The beetles of the family Tenebrionidae, often referred to as the darkling beetles, are a diverse bunch. Members of this family have adapted to a wide range of lifestyles, coming in a variety of body types. Among the more obscure representatives of the tenebrionids are the members of the Southern Hemisphere tribe Titaenini.

Titaena sp., copyright Martin Lagerwey.

Members of the Titaenini have a typical Gondwanan distribution, being known from southern and eastern Australia, New Zealand, New Caledonia and southern South America (Matthews & Bouchard 2008). They grow up to about a centimetre and a half in length with an elongate, parallel-sided body shape that is more or less cylindrical. The prothorax is relatively short, allowing the head to be held vertically in the Australian genus Titaena. Antennae are short with fairly simple segments not forming a club at the end. Legs have similarly simple tarsi. The tribe is distinguished from other, similar darkling beetles by the epipleura (the flattened underside of the elytral margins) which are shortened, not reaching the elytral apex. Members of the Titaenini have large repugnatorial glands opening near the end of the abdomen. In the Australian genus Titaena, at least, species are usually metallic blue or green in coloration.

The habits of the Titaenini are poorly known. As far as we do know, their larvae are specialised feeders on lichen. Adults probably pursue a similar diet. This is an exposed lifestyle, one in which you could easily come to the attention of predators, and the bright coloration of Titaena probably functions to warn off any such unwelcome interest.

REFERENCE

Matthews, E. G., & P. Bouchard. 2008. Tenebrionid Beetles of Australia: Descriptions of tribes, keys to genera, catalogue of species. Australian Biological Resources Study: Canberra.

A Spider for Christmas

Hasselt's spiny spider Macracantha hasselti, copyright Patrick Randall.

In many warmer parts of the Old World, the spiny orb-weavers of the subfamily Gasteracanthinae are among the most eye-catching of all spiders. As well as constructing complex, easily seen webs in the manner of other orb-weavers, these spiders draw attention by their bright colours and ornate structure, often with prominent arrangements of spines on the abdomen. Here in Australia, their dramatic appearance has lead to their often being referred to as "Christmas spiders". The exact reason for this drama is uncertain. The spines are generally presumed to be for defence but the coloration has been subject to multiple proposals from an aposematic warning to functioning as a lure for flying insects.

Variants of Gasteracantha kuhli, from Macharoenboon et al. (2021).

The taxonomic history of the Christmas spiders is a complicated one, going back to the early years of arachnology. Not surprisingly for such distinctive animals, a large number of species were described by early authors. However, species of spiny orb-weavers are often very variable, leading to a significant number being described as new on more than one occasion. As with other orb-weavers, males are much smaller than females, and the spines on the abdomen tend to be more poorly developed. Coloration within a species can vary considerably in brightness, tone, and patterning. Structural features such as the arrangement of spines and the development of sigilla (impressions on the dorsal surface of the abdomen that mark the placement of internal muscles) can still provide reliable indicators of species identity, as (of course) can features of the genitalia. You have to learn to look past the superficial daubings and focus on the underlying form.

Give Plateosaurus Its Due

You could make a fascinating study (and many have) just looking at the history of which dinosaurs have held the foreground of popular culture when. The Iguanodon and Megalosaurus of the late 1800s, the Trachodon and Palaeoscincus of the earlier 1900s, the stratospheric rise of Velociraptor (sensu lato) with the release of Jurassic Park. And then there are those that never quite seem to get their dues. I've commented before on the odd relegation of Camarasaurus to the status of also-ran among famous sauropods. But perhaps the ultimate example of a dinosaur forced unfairly to the background is the should-be darling of the Late Triassic, Plateosaurus.

Plateosaurus 'engelhardti' in the Sauriermuseum at Frick, copyright Ghedoghedo.

Plateosaurus should, by all rights, be a superstar of dinosaur pop-culture. It was one of the first dinosaurs to reach massive size, extending up to nine metres in length and probably standing about as high (or slightly higher) than a tall man at the withers (Yates 2003). It is known from literally hundreds of specimens, many of them with large parts of the skeleton preserved, representing ages from juvenile to full maturity. Some of the bonebeds where it is found contain little but Plateosaurus and may have been formed in dramatic mass mortality events. Plateosaurus is easily the best known of the basal Sauropodomorpha, the 'prosauropods'. And yet, though Plateosaurus regularly appears in popular depictions, it rarely seems to make much more than a brief cameo. Why is this the dinosaur that gets no respect?

In part, it may be because it comes from a time period that gets less attention as a whole. The Triassic tends to get seen as a meer prelude to later, more 'exciting' parts of the Mesozoic. Plateosaurus itself, together with the other 'prosauropods', tends to also get overshadowed by its later, more eye-catching relatives, the sauropods. And when you get down to it, Plateosaurus may also be let down by the fact that it is perhaps the single most average dinosaur you could possibly imagine. Honestly, if you asked someone to depict a truly generic dinosaur, I don't think it would come out looking too different from Plateosaurus.

Reconstructed Plateosaurus, albeit in a now-obsolescent quadrupedal pose, copyright Elekes Andor.

All these criticisms aside, Plateosaurus is still a fascinating genus. Its remains have been found across central Europe, in Germany, Switzerland and France. The exact number of species in the genus has long been uncertain. As with other early-named dinosaur genera, 19^th Century palaeontologists named several species whose application has been subject to debate. Yates (2003) recognised two species in the genus, the earlier and smaller P. gracilis, and a larger, later species that Yates labelled P. engelhardti but which, due to various taxonomic shenanigans, should probably now be called P. trossingensis. Plateosaurus trossingensis is the better known of the two species, known from extensive bone-beds found at Trossingen and Halberstadt in Germany, and Frick in Switzerland (Lallensack et al. 2021). Some have questioned whether all these bone-beds represent a single species but Lallensack et al. found that examination of skulls from different locations failed to identify specific distinctions. Both Plateosaurus species would have been among the largest land animals of their times; even the smaller P. gracilis may have still reached lengths of five or six metres. Plateosaurus had a relatively long, narrow head though comparison of this feature with other prosauropods may be complicated by post-mortem distortion.

The life posture of Plateosaurus has historically been the subject of much dispute, whether it was bipedal, quadrupedal, or shifted freely between the two. However, recent models of the range of movement of the Plateosaurus hand and fore-arm have concluded that it was incapable of turning its hands palm-downwards, so it could not have supported itself comfortably on its fore limbs (Reiss & Mallison 2014). Obviously, the capacity for quadrupedal locomotion would evolve at some point in sauropodomorph evolution (in this day and age, I don't think anyone is proposing bipedal sauropods) but it was not before Plateosaurus.

Skeletal reconstruction of Unaysaurus talentinoi, copyright Maurissauro.

The phylogenetic relationships of Plateosaurus to other sauropods have been similarly disputed. Plateosaurus is, of course, the type genus of the family Plateosauridae but the concept of that family has varied significantly over time. For a large part of the twentieth century, 'Plateosauridae' was kind of a catch-all for all moderately large prosauropods, with Anchisauridae for the smaller species and Melanorosauridae for the giants. Redefinition of Plateosauridae to include only close relatives of Plateosaurus have significantly winnowed its contents. The current closest known relative of Plateosaurus is the recently described Issi saaneq, based on a pair of near-complete skulls from Greenland (Beccari et al. 2021). This species is close enough to Plateosaurus that its remains were previously assigned to P. englehardti. Offhand, "issi saaneq" is translated by the species' authors as "cold bone" in the local Kalaallisut language, but this looks to be another situation like "mei long" where a phrase was converted into a species name without considering that noun and descriptor order is reversed in biological names.

Other likely plateosaurids include two South American species, Unaysaurus tolentinoi and Macrocollum itaquii. The status of an Indian species Jaklapallisaurus asymmetrica is more uncertain. Beyond this, things become increasingly dodgy with little agreement over the details of prosauropod phylogeny. The overall conservative appearance of prosauropods means that phylogenetic studies are heavily reliant on fine details of the osteology that are debated between authors or not preserved in key taxa. Nevertheless, it does appear that the plateosaurids were widespread in the Norian epoch of the Triassic, and are bound to catch the attention of time travellers to the period.

REFERENCES

Beccari, V., O. Mateus, O. Wings, J. Milàn & L. B. Clemmensen. 2021. Issi saaneq gen. et sp. nov.—a new sauropodomorph dinosaur from the Late Triassic (Norian) of Jameson Land, central east Greenland. Diversity 13: 561.

Lallensack, J. N., E. M. Teschner, B. Pabst & P. M. Sander. 2021. New skulls of the basal sauropodomorph Plateosaurus trossingensis from Frick, Switzerland: is there more than one species? Acta Palaeontologica Polonica 66 (1): 1–28.
Reiss, S., & H. Mallison. 2014. Motion range of the manus of Plateosaurus engelhardti von Meyer, 1837. Palaeontologica Electronica 17 (1): 12A.

Yates, A. M. 2003. The species taxonomy of the sauropodomorph dinosaurs from the Löwenstein Formation (Norian, Late Triassic) of Germany. Palaeontology 46 (2): 317–337.

The Hairy Digger Wasps of Hong Kong

Taylor, C., & C. Barthélémy. 2021. A review of the digger wasps (Insecta: Hymenoptera: Scoliidae) of Hong Kong, with description of one new species and a key to known species. European Journal of Taxonomy 786: 1–92.

On Christmas Eve, I received an e-mail from Christophe Barthélémy in Hong Kong to tell me that we'd gotten a Christmas present. Our big paper on the scoliid wasps of Hong Kong was now freely, publicly available! In this paper, we reviewed all sixteen species of Scoliidae known from the Hong Kong SAR to date, providing detailed descriptions and photographs of each. Nine of these had not previously been recorded from the region; one represented an entirely novel species. We also provided a detailed identification key and clarified some of the often convoluted taxonomy of this family.

Liacos erythrosoma, one of the larger scoliid species found in Hong Kong, copyright Jeffrey Cfy.

The Scoliidae, sometimes referred to as the hairy digger wasps or hairy flower wasps, are often large, striking wasps (the largest species found in Hong Kong get close to an inch in length) that are most often seen by observers when they visit flowers for food. They differ from other wasps in the structure of the wings which are shaped into radiating folds (often referred to as 'pseudoveins') towards the outer margins. In life, the wings have an iridescent appearance. Female scoliids are robust insects with powerful legs. This is so they can burrow into the ground in search of hosts for their larvae which develop as parasitoids on the larvae of scarabaeid beetles. Male scoliids are generally smaller and more slender than females. In some species (particularly members of the tribe Campsomerini), males can look very different from females, to the extent that it can be all but impossible to link one with the other in isolation. Males of some species can sometimes be found in large numbers as they form swarms in search of females.

Mating pair of Phalerimeris phalerata (male on top), perhaps Hong Kong's commonest scoliid species. Copyright Daphne Wong.

Christophe and I had lit upon the idea of producing a review of the family as I was attempting to identify specimens collected as part of the Hong Kong mangrove survey. Christophe already had an extensive number of scoliids as part of his own amateur collection; these formed the greater part of the material we used. One of our primary challenges was making sense of the group's taxonomy. As well as the aforementioned difficulties in matching males to females, scoliid taxonomy has its own individual tangles. The system has historically been beset with confusion, questionable decisions, and disregard for priority. Species have often been subdivided into a bewildering array of subspecies, varieties and formae, often on the basis of quite superficial differences and often with little apparent consideration as to whether they represented distinct populations (individuals of different 'subspecies' may often be found at the same location). As a result, I had to spend a lot of time digging into archaic publications to make sure they had been correctly quoted by their successors. Fortunately (as long time readers of this site will probably know), this is exactly the sort of thing that I love doing*.

*With a shout-out here to the Biodiversity Heritage Library. An absolutely brilliant resource that has just revolutionised the way we do literature research.

While I mostly took care of the taxonomy, key, and the first drafts of the descriptions, Christophe produced the photos, distribution maps, and revisions of the descriptions after I returned to Australia (including male genital dissections of all the species we had on hand). The end result is a paper I feel very proud of. Thank you to Benoit Guénard and the Entomology lab of Hong Kong University for providing access to resources, and if you have any interest in the wonderful world of Hong Kong hairy flower wasps, you can check out the final product here.

The Pelecocrinidae

The latter part of the Palaeozoic represented a peak in crinoid diversity. More families of crinoid have been recognised from the Carboniferous and Permian than any period before or since. Among the various families of the Late Palaeozoic were representatives of the Pelecocrinidae.

Pelecocrinus insignis, from Moore & Teichert (1978).

The fossil record of the pelecocrinids was long-lasting but patchy. They are known from the early Carboniferous of North America (Pelecocrinus) and Great Britain (Forthocrinus), the late Carboniferous of North America (Exoriocrinus), and the late Permian of Italy (Tetrabrachiocrinus) and Indonesia (Drepaocrinus, Malaiocrinus). These locations largely correspond to what would have been a distribution along the northern coast of the Palaeotethys Ocean, possibly becoming extinct in the west as the gap between North America and the southern continent of Gondwana closed to form the Pangean supercontinent. Pelecocrinids seem to be so far unknown from the southern continents.

In life, pelecocrinids were characterised by a high crown arising from a low, bowl-shaped cup. The stem could be round or pentagonal. The base of the cup was flattened or shallowly concave, so the infrabasals (the lowest circle of plates above the stem) were barely or not visible where the cup to be observed from the side. The articulations between the upper plates of the cup and the bases of the arms were angled downwards and outwards with the articular facets being somewhat narrower than the plates they sat on. The arms themselves had a wedge-shaped cross-section and divided into equal branches two or more times along their length. Each arm bore one or two rows of pinnules. The anal sac, as described for Pelecocrinus, was relatively short and slender and summited by heavy, spinose plates.

The structure of the arm articulations and pinnules indicates that the arms would have been subject to muscular control with individual arms being able to be moved in more than one plane. This arrangement became increasingly common among crinoids from the Carboniferous onwards, allowing them to function in more high-current habitats. The position of the arms and pinnules could be adjusted to optimise filtration from the water column, while the current provided lift to the crown so it did not need to be mechanically supported by the stem alone. The effectiveness of this arrangement is attested to by the long history of the pelecocrinids. Nevertheless, the end-Permian extinction was to end their lineage along with that of so many of their contemporaries.

REFERENCE

Moore, R. C., & C. Teichert (eds) 1978. Treatise on Invertebrate Paleontology pt T. Echinodermata 2. Crinoidea vol. 2. The Geological Society of America, Inc.: Boulder (Colorado), and The University of Kansas: Lawrence (Kansas).