Bye, Bye, Spinicrus

Female Spinicrus...no, sorry, Megalopsalis nigricans, photographed by Tony.

I've just had a paper out. The funny thing is, it's making me feel both pleased yet a little maudlin, because it represents something of an end of an era. The last part of my PhD thesis has been published. The last remnant of my student days has been cast off. I think I need a hug.

The paper in question is: Taylor, C. K. 2013. Further revision of the genus Megalopsalis (Opiliones, Neopilionidae), with the description of seven new species. ZooKeys 328: 59-117. It's open access, so go take a squizz. One thing that I also can't resist pointing out, though I don't know if it really makes much difference because it's a primarily online journal and hardly anyone will see the print issue: it's one of my images on the cover.

Technically, this paper represents my long-awaited (by me, at least) revision of the harvestman genus Spinicrus. In the end, though, I had to change the title of the paper, because on of the main results of this revision was that Spinicrus became a synonym of the older genus Megalopsalis. In an earlier publication, I cut Megalopsalis down to size by removing its New Zealand species to a new genus, Forsteropsalis. But now it's back, and stronger than ever before!

Female Megalopsalis tasmanica, the erstwhile Spinicrus tasmanicum. Another photograph from Tony.

Previously, Spinicrus was primarily separated from Megalopsalis by one feature: the presence of a side branch on one of the segments of the pedipalps of Megalopsalis. Taxonomists tend to be wary of defining a group purely by the absence of features. It implies that the members of that group are united more by the idea that they just don't belong in any other group, rather than anything that actually connects them per se. So, in this case, Megalopsalis was the species with a pedipalp side-branch, and Spinicrus was... the rest. It also didn't help matters that a pedipalp side-branch is something that has evolved and de-evolved a number of times within harvestmen, leading to a bit of questioning about its significance. A few years ago, I separated a few of the more distinctive 'Spinicrus' as the genus Neopantopsalis. This made Spinicrus a bit less heterogeneous but still didn't solve the underlying issue. It just meant that now you took out Megalopsalis and took out Neopantopsalis, and Spinicrus was still... the rest.

The answer, as so often in invertebrate taxonomy, came largely from the boy bits. When I looked at the male genitalia, I found that Megalopsalis and Spinicrus species shared a similar penis morphology, in which the end of the penis was fairly short, flat and shaped more or less like a rounded triangle:

This is what a 'Spinicrus' stewarti penis looks like.
In contrast, the end of the penis in Neopantopsalis species is longer, as demonstrated by N. thaumatopoios:

Put these features into a phylogeny of the family that these genera belong to (Neopilionidae), and I overall ended up with this:

Consensus of various phylogenetic analyses under various parameters (numbers at nodes represent the percentage of analyses in which that clade was recovered). Taxa coloured green are what would have been called 'Spinicrus' previously, while those in red would have been 'Megalopsalis'.

Note that this is a bit of a faux phylogeny, because it's a comparative summary of separate analyses under separate parameters (see the paper for details). Only those clades marked with a 100 were supported in all analyses. The important detail is the distribution of the green 'Spinicrus' relative to the red 'Megalopsalis': no matter what the analytical conditions, 'Megalopsalis' was always nested well within 'Spinicrus'. Indeed, under most conditions, 'Megalopsalis' was polyphyletic within 'Spinicrus'. Because of this, and because of the lack of any positive uniting features for Spinicrus species that were not also present in Megalopsalis, I felt the best course of action was to declare the two genera synonyms. Also subsumed under Megalopsalis was Hypomegalopsalis, a species that I had earlier established for a single species of uncertain affinities (Megalopsalis tanisphyros in the tree above). At the time, I commented that, "if anyone conducts a further study in the future that supports quashing Hypomegalopsalis, I won't be protesting". The fact that I got to do that myself just makes me all the happier.

There's a lot more I could talk about here, but I'm sure you all stopped reading long ago. Just go to the paper.

The Antedoninae: (Relatively) Big-Bellied Feather Stars

Several individuals of Antedon bifida attached to a kelp stipe, photographed by Bernard Picton.

The feather stars and other crinoids are both the most divergent and least known of the modern echinoderms. This is the second post here at Catalogue of Organisms on modern feather stars; an earlier post gave a brief overview of some of the details of the feather star lifestyle and anatomy. The main subject of the earlier post was the family Charitometridae; this post will focus on a different group, the Antedoninae. Yes, Virginia, there are different varieties of feather star.

The Antedonidae and related families differ from most other feather stars in that the internal cavity of the centrodorsal, the plate that forms the base of the calyx (central cup) of the feather star, is relatively large compared to the centrodorsal's diameter (in life, this cavity has organs nestled in it). When the antedonids were reviewed by the American echinodermatologist Austin H. Clark (Clark & Clark 1957*), he regarded this difference as significant enough to treat the antedonids and related families as a separate group, the Macrophreata, from other families in the Oligophreata with only a small centrodorsal cavity. However, later researchers have downplayed the significance of this distinction (e.g. Wienberg Rasmussen 1978), and even the monophyly of the Antedonidae has been questioned. Well-developed muscular articulations in the upper part of the calyx also indicate that antedonids are generally stronger swimmers than other feather stars (Meyer 1972). Clark & Clark (1967) divided the antedonids between six subfamilies, but Ailsa Clark commented that the distinctions between subfamilies were not always clear.

*Austin Clark's epic revision of the living crinoids was left incomplete after his death in 1954, until it was taken up by the British researcher Ailsa Clark (no relation, as far as I've found). The section of Clark's monograph on the 'Macrophreata' therefore made its debut under both researcher's names.

Specimen of Dorometra photographed by Lyle Vail and Anne Hoggett. The page linked notes that this species swims actively when disturbed, before 'holding their arms above the disk to form a shuttlecock shape and then plummeting towards the bottom'.

The Antedoninae generally differ from other antedonids in having rather short cirri (though the Philippine species Eumetra chamberlaini has exceptionally long cirri, up to about a third of the length of its arms). The cirri are also rounded dorsally, without dorsal spines or ridges, and most species lack ventral spines except one on the penultimate segment of the cirrus that opposes the terminal claw. The centrodorsal is low and rounded in the majority of species, though it may become raised and closer to conical. Antedonines include some of the shallowest-living of recent crinoids, with some species even found in tide pools; the deepest-living antedonines are known from 932 m. Clark and Clark (1967) recognised ten genera within the Antedoninae; a fossil genus Palaeantedon (from the Eocene to Quaternary) was listed in addition to the Recent genera by Wienberg Rasmussen (1978), and an eleventh Recent genus Ctenantedon was described by Meyer (1972).

The rosy feather star Antedon bifida and the Mediterranean feather star A. mediterranea are among the best-studied of all feather stars, primarily due to both being found in shallow waters around Europe. However, the greater diversity of antedonines is known from the Indo-Pacific. Apart from species of Antedon, the only Recent antedonine known from the Atlantic is the Caribbean Ctenantedon kinziei (the fossil species of Palaeantedon are also Atlantic). Characters used to distinguish genera include features of the pinnules, the slender side-branches of the arms. Antedon species, for instance, usually have the second and third pinnules on each arm similar in size to each other, and both distinctly shorter than the first pinnule. Ctenantedon kinziei is unusual in having a comb of 'teeth' developed in the distal part of the proximal pinnules. The function of these teeth is not entirely certain, though Meyer (1972) noted that he had observed the oral pinnules of comasterid feather stars (which also bear similar teeth) moving in and out from the central disk in a manner that suggested they were being used to remove undigested food and other waste material.

REFERENCES

Clark, A. H., & A. M. Clark. 1967. A monograph of the living crinoids. Volume 1. The comatulids. Part 5—suborders Oligophreata (concluded) and Macrophreata. Smithsonian Institution, United States National Museum, Bulletin 82.

Meyer, D. L. 1972. Ctenantedon, a new antedonid crinoid convergent with comasterids. Bulletin of Marine Science 22 (1): 53-66.

Wienberg Rasmussen, H. 1978. Articulata. In Treatise on Invertebrate Paleontology pt. T. Echinodermata 2. Crinoidea (R. C. Moore & C. Teichert, eds) vol. 3 pp. T813-T927. The Geological Society of America, Inc.: Boulder (Colorado), and The University of Kansas: Lawrence (Kansas).

Paradrillia

Paradrillia patruelis, from Joop Trausel and Frans Slieker.

Paradrillia is a genus of conoid gastropods found in the Indo-Pacific region, with a fossil record going back to the Miocene (Powell 1966; previous CoO posts on conoids can be found here, here, here and here). Species of Paradrillia are small shells, about one to three centimetres in length, with a relatively tall spire and short siphonal canal. The sculpture on the outside of the shell usually consists of nodular spirals; the operculum is leaf-like, with a terminal nucleus. The long, awl-shaped radular teeth are trough-shaped in cross-section (Kilburn 1988).

Paradrillia regia, from G. & Ph. Poppe.

The classification of Paradrillia has shifted around over the years, like most of the less differentiated conoids that were lumped by Powell (1966) under the heading of 'Turridae'. Powell (1966) classed them as Turriculinae, Kilburn (1988) transferred them to the Stictispirinae. Kilburn also synonymised Powell's separate genera Paradrillia and Vexitomina. Powell had distinguished them on the basis that Paradrillia supposedly had an operculum with a mediolateral nucleus instead of the terminal nucleus of Vexitomina. However, this was based on a single specimen that Kilburn regarded as teratological after he found terminal nuclei in Paradrillia melvilli. Most recently, Paradrillia was placed by by Bouchet et al. (2011) on the basis of molecular data in their new family Horaiclavidae.

REFERENCES

Bouchet, P., Yu. I. Kantor, A. Sysoev & N. Puillandre. 2011. A new operational classification of the Conoidea (Gastropoda). Journal of Molluscan Studies 77: 273-308.

Kilburn, R. N. 1988. Turridae (Mollusca: Gastropoda) of southern Africa and Mozambique. Part 4. Subfamilies Drilliinae, Crassispirinae and Strictispirinae. Annals of the Natal Museum 29 (1): 167-320.

Powell, A. W. B. 1966. The molluscan families Speightiidae and Turridae: An evaluation of the vaid taxa, both recent and fossil, with lists of characteristic species. Bulletin of the Auckland Institute and Museum 5: 1-184.

Beetle Flies

Unidentified celyphid, photographed by Giovzaid85.

Those of you who follow me on Twitter (@CatofOrg) may have already seen these guys, but I thought it worth putting them up here as well. Because sometimes you come across an animal that just makes you stop, blink, and exclaim, "What the creeping jayzus is that!". Ladies and gentlemen, the Celyphidae.

Another celyphid, photographed by Melvyn Yeo.

Celyphids are flies that are doing their damnedest to look like a beetle (and are hence, unsurprisingly, commonly known as beetle flies). The scutellum, which in most flies is a relatively small lobe of the thorax sitting behind and between the wings, has become massively enlarged and overtops the abdomen. The wings (which are full-sized and fully functional) slip in underneath the scutellum when folded back. Just to add to the overall beetle-osity of the thing, celyphids can be very shiny and metallic (check out the blue-black item here). The function of this giant scutellum is unknown; protection is the first thing that comes to my mind, but I don't know if the scutellum is any more sclerotised than the rest of the animal. One suggestion that has apparently been made is that the scutellum may provide extra buoyancy in flight (Tenorio 1972), to which I ask, is it hollow or something?

Photo by Meng Foo Choo.

Celyphids are found in tropical Asia and Africa (all the photos on this page except the last were taken in Singapore). They are closely related to the more widespread family Lauxaniidae, and have been treated by at least some authors as a derived subgroup of the latter (some lauxaniids also show a degree of enlargement of the scutellum). The larvae of celyphids feed on rotting vegetation.

Celyphus koannanius, from here.

REFERENCE

Tenorio, J. M. 1972. A revision of the Celyphidae (Diptera) of the Oriental Region. Trans. R. Ent. Soc. Lond. 123 (4): 359-453.

Yponomeutoids and their Boring Larvae

...because some puns will never die.

Larvae of the bird-cherry ermine moth Yponomeuta evonymella, from here.

As noted in an earlier post, most people's perception of Lepidoptera, 'butterflies and moths', is heavily skewed towards the larger members of the group while the greater diversity is actually to be found among the smaller species (this sentence, offhand, could be repurposed for just about any animal group). The subject of today's post, the Yponomeutoidea, are a clade of about 1800 species of the much-overlooked smaller Lepidoptera. Yponomeutoids have been recognised as a group primarily on the basis of a single synapomorphy, the presence of posterior lobes on the eighth abdominal pleura (a 'pleuron' being a sclerite on the side of the body wall). This character has been secondarily lost in some subgroups of the Yponomeutoidea, but the clade is also supported by molecular data (Sohn et al. 2013). The larvae of yponomeutoids are plant-feeders, with the clade including some species that feed internally as leaf-miners or stem-borers, and others that feed externally on leaves though they do conceal themselves within a silk webbing. A number of species are effectively both, starting out as internal leaf borers then changing to external leaf webbers as they grow larger. Some species are notable horticultural pests, such as the diamondback moth Plutella xylostella that attacks brassicas*.

*Horticulture is the only human endeavour in which you will hear something described as 'attacking' a cabbage.

Apple leaf miner Lyonetia clerkella, photographed by Jeff Higgott.

The most recent review of the clade's systematics by Sohn et al. (2013) recognised eleven families within the Yponomeutoidea, but this was not the first re-organisation of the yponomeutoids and it will probably not be the last. Many of the families have few distinct synapomorphies, and a few recognised by Sohn et al. lack recognised morphological synapomorphies altogether and are united by molecular analysis only. Most yponomeutoids follow the usual microlepidopteran pattern of being small and generally brown, but there are some exceptions. The 'mega-plutellids' of New Zealand and Tasmania (placed by Sohn et al. in the family Glyphipterygidae rather than Plutellidae) are relatively large, with the Tasmanian Proditrix nielseni having a wingspan of over six centimetres (McQuillan 2003). The adult of the ailanthus webworm Atteva pustulella has a fairly striking array of black-ringed white patches on an orange background.

Galapagos bitterbush moth Atteva hysginiella, photographed by Rich Hoyer.

Though the clade is diverse in its habits overall, feeding habits tend to be conserved within each of the constituent families. It is not entirely clear whether internal or external feeding represents the original lifestyle of the yponomeutoids, though there may be a slight tip towards internal feeding. If this is the case, then external feeding has arisen within the yponomeutoids on a number of occasions, and the pine needle miners of the genus Zelleria in the family Yponomeutoidea probably represent at least one case of a internal feeder derived from externally feeding ancestors. Some families show a bias towards particular plant hosts: the Attevidae are primarily found on Simaroubaceae, while the Bedeliidae show a preference for Convolvulaceae. Others are more diverse in their selection.

REFERENCES

McQuillan, P. B. 2003. The giant Tasmanian ‘pandani’ moth Proditrix nielseni, sp. nov. (Lepidoptera: Yponomeutoidea: Plutellidae s. l.) Invertebrate Systematics 17: 59-66.

Sohn, J.-C., J. C. Regier, C. Mitter, D. Davis, J.-F. Landry, A. Zwick & M. P. Cummings. 2013. A molecular phylogeny for Yponomeutoidea (Insecta, Lepidoptera, Ditrysia) and its implications for classification, biogeography and the evolution of host plant use. PLoS One 8(1): e55066. doi:10.1371/journal.pone.0055066.

Majids: Crabs with Stylish Hats

Aggregation of large spider crabs Leptomithrax gaimardii, photographed by Peter Fuller.

The subjects of today's post, the Majidae, commonly go by the names of spider crabs or decorator crabs. The first of those names might sound like some people's ultimate nightmare, but I doubt that anyone could complain about the latter. Majids are characterised by having a carapace longer than wide, often with a covering of bristly hooked setae and relatively long legs (hence the name 'spider crab'). They get their alternate name of 'decorator crab' from the habit of many species of using the aforementioned hooked setae to attach algae and other bits of organic matter to themselves. The primary purpose of this adornment is to provide camouflage, and a decorated spider crab can be inordinately difficult to see when not moving. A secondary use of the crab's organic covering, however, is that they will also feed on material from it in times of need*.

*It is perhaps fortunate for Gaga that the question was never raised of her doing the same.

Triangle crab Eurynolambrus australis, from here.

The circumscription of the Majidae is more than a little fluid: at times, it has been used to include all the spider crabs of the superfamily Majoidea, but the more common practice these days is to divide the majoids between a number of families. Unfortunately, authors have disagreed about what those families should be. Ng et al. (2008) united the subfamilies Majinae and Mithracinae within the Majidae on the basis of shared features such as a well-developed protective orbit around the eyestalk. However, a direct relationship between majines and mithracines is not currently supported by molecular (Hultgren & Stachowicz 2008) or larval (Marques & Pohle 1998) data, though both these latter data sources are themselves limited by the relatively small number of studied taxa. Two smaller subfamilies included by Ng et al. (2008) in the Majidae, the Planoterginae and the isolated species Eurynolambrus australis, have not yet been analysed molecularly. Eurynolambrus australis is a particularly unusual little majid, so much so that it looks more like a parthenopid than a majid. Eurynolambrus also lacks hooked setae and so does not decorate itself; instead, it relies for disguise on its resemblance in colour to the coralline algae amongst which it lives (and on which it primarily feeds, though it is omnivorous overall—Woods & McLay 1996). Ng et al. placed it in the Majidae nevertheless owing to the resemblance of its larval stages to those of Majinae.

Channel clinging crab Mithrax spinosissimus, photographed by Nick Hobgood.

The two main subfamilies, the Majinae and Mithracinae, can be distinguished by the development of the orbit around the eyestalk. In the Mithracinae, the orbit is broadly expanded both above and below (with the lower margin formed from an expansion of the basal antennal segment), almost entirely enclosing the eyestalk and giving the front of the carapace a distinctly broad appearance in dorsal view. In the Majinae, the basal antennal segment is not expanded to form an underside to the orbit, so the eyestalks are contained from above only (Davie 2002). The Majinae are most diverse in the Indo-West Pacific, with only a handful of genera found outside this region. Some majines are quite large: the Australian Leptomithrax gaimardii reaches a leg-span of about 70 cm. The Mithracinae are more pantropical inhabitants of shallow water reefs.

REFERENCES

Davie, P. J. F. 2002. Zoological Catalogue of Australia vol. 19.3B. Crustacea: Malacostraca: Eucarida (part 2): Decapoda—Anomura, Brachyura. CSIRO Publishing: Collingwood (Australia).

Hultgren, K. M., & J. J. Stachowicz. 2008. Molecular phylogeny of the brachyuran crab superfamily Majoidea indicates close congruence with trees based on larval morphology. Molecular Phylogenetics and Evolution 48: 986-996.

Marques, F., & G. Pohle. 1998. The use of structural reduction in phylogenetic reconstruction of decapods and a phylogenetic hypothesis for 15 genera of Majidae: testing previous larval hypotheses and assumptions. Invertebrate Reproduction and Development 33 (2-3): 241-262.

Ng, P. K. L., D. Guinot & P. J. F. Davie. 2008. Systema brachyurorum: part I. An annotated checklist of extant brachyuran crabs of the world. Raffles Bulletin of Zoology 17: 1-286.

Woods, C. M. C., & C. L. McLay. 1996. Diet and cryptic colouration of the crab Eurynolambrus australis (Brachyura: Majidae) at Kaikoura, New Zealand. Crustacean Research 25: 34-43.

The Legacy of Rhampsinitus

According to the Histories of Herodotus, Rhampsinitus was a pharaoh of Egypt who ordered the construction of a secure storehouse for his wealth. However, the architect in charge of the storehouse's construction installed a secret entrance into it without the pharaoh's knowledge. The architect later told his two sons about the secret entrance, which they then used to help themselves to a share of the pharaoh's treasure. Unable to detect how the thieves were getting in, Rhampsinitus ordered a man-trap to be placed inside the storehouse, and the next time the thieves got in, one of them was caught by the trap. As there was no chance of escape, the remaining thief cut off his brother's head to prevent identification. Nevertheless, Rhampsinitus held onto the headless body and ordered his soldier's to look out for anyone showing signs of recent bereavement.

Through a ruse involving a pair of donkeys, a cartload of wine and some arguably irresponsible guards, the thief was able to recover his brother's body from the pharaoh, escaping both capture and his mother's complaints about his brother's mistreatment. Rhampsinitus therefore came up with another scheme to catch the thief: he ordered his daughter to offer herself up in a brothel to whoever would tell her the greatest misdeed he had committed. The thief did indeed confess his crimes to the daughter, who was apparently just that enticing. But when she attempted to grab hold of him and call for the guards, he escaped by palming a hand cut from a body that he had hidden up her sleeve. When he was told how the thief had eluded him again, Rhampsinitus was so impressed by the man's audacity and cunning that he ordered him pardoned. When the man came forward, Rhampsinitus gave him his daughter for a wife.

Male Rhampsinitus hispidus, from Roewer (1923). This would appear to be a species that lives up to its name; others are not quite so flagrantly spinose.

Modern historians agree that Rhampsinitus probably never existed, at least not as he was portrayed by Herodotus (while the accusation that Herodotus was the 'father of lies' is more than a little unfair, it must be admitted that he was not always one to let a little thing like historical accuracy stand in the way of a good story). Nevertheless, his name lives on today in southern Africa: in 1879, the French arachnologist Eugene Simon gave the name Rhampsinitus to a genus of long-legged harvestmen. Simon did not give any explanation for his choice, and it is possible that there was no direct reason: many authors gave random classical names to genera. Alternatively, it may be that the crown of denticles on the eyemound of this genus inspired Simon to give it a suitably regal name.

The long-legged harvestman fauna of sub-Saharan Africa is dominated by members of the subfamily Phalangiinae, which largely have the region to themselves except a few relictual Neopilionidae restricted to the southernmost part of the continent. Rhampsinitus is currently the largest recognised genus of African phalangiines, with over forty species. The centre of diversity for the genus is in the southern region, but it extends north to Zaire, Uganda and Kenya (possibly to Somalia, though the assignment of the Somalian species to Rhampsinitus has been questioned—Staręga 2009). Rhampsinitus is one of a group of African phalangiines (including Guruia and Dacnopilio, but not Cristina) in which the males have enlarged chelicerae similar to those of Australasian 'monoscutids'*. In the absence of a formal phylogenetic study of the Phalangiinae, it remains an open question whether these large-chelicerate genera form a clade. Schönhofer (2008) looked briefly at variation in male chelicera length (which can be considerable) within one species, Rhampsinitus transvaalicus; his results suggest an allometric relationship between body size and chelicera length for this species at least.

*A few years back, I was sent a pile of 'monoscutids' from the California Academy of Sciences to identify. While they're still waiting for me in the cupboard (sorry, guys!), I could see when I unpacked them that many were in fact African phalangiines that had been misidentified due to this character.

Relationship between altitude and eyemound ornamentation, as illustrated by Kauri (1961).

A number of species in this genus have interesting distributions, often related to altitude. Thus, in South Africa, Rhampsinitus leighi is found in lowland habitat from sea level to 800 m, while R. transvaalicus inhabits montane forest above 1200 m (Staręga 2009). Kauri (1961) made a comparison of morphometrics and altitude in South African Rhampsinitus: montane species had much shorter legs relative to body size than the lowland R. leighi. There was also a difference in development of ornamentation: R. maculatus, collected at 10,000 feet above sea level, had the denticles on the eyemound reduced to mere spicules, in contrast to the ornate, almost antler-like outgrowths of R. leighi.

REFERENCES

Kauri, H. 1961. Opiliones. In: Hanström, B., P. Brinck & G. Rudebeck. South African Animal Life: Results of the Lund University Expedition in 1950–1951 vol. 8 pp. 9–197. Almqvist & Wiksell: Uppsala.

Schönhofer, A. L. 2008. On harvestmen from the Soutpansberg, South Africa, with description of a new species of Monomontia (Arachnida: Opiliones). African Invertebrates 49 (2): 109-126.

Staręga, W. 2009. Some southern African species of the genus Rhampsinitus Simon (Opiliones: Phalangiidae). Zootaxa 1981: 43-56.