Field of Science

Walruses, Sea Lions and Fur Seals

Adaptation to a primarily aquatic lifestyle has happened numerous times within mammals, but some groups have radiated more in this environment than others. One particularly well-known group of marine mammals is the pinnipeds, the seals and sea lions.

Australian sea lions Neophoca cinerea on a beach on Kangaroo Island, copyright Diver Dave.


Pinnipeds are highly modified for life in the water, with streamlined bodies and all four limbs modified into flippers. When I was young, many of the animal books that I read referred to pinnipeds as their own distinct order within the mammals. However, it has long been recognised that pinnipeds are derived from within the Carnivora and these days they are almost universally treated as a subgroup of the latter. Modern pinnipeds are divided between three families: the Phocidae ('true' seals), Otariidae (fur seals and sea lions) and Odobenidae (which has only one living species, the walrus Odobenus rosmarus). While some morphological analyses have argued for a relationship between the walrus and the Phocidae, the majority view treats the walrus and the Otariidae as together forming a clade Otarioidea, commonly referred to as the eared seals. There has historically also been some argument about whether the pinnipeds represent a single clade; some have argued for two separate origins, Otarioidea being related to bears whereas Phocidae were supposed to be closer to otters and weasels. However, the current majority supports a single origin for the group.

Northern fur seals Callorhinus ursinus, photographed by M. Boylan.


Eared seals differ from true seals in the possession of small external ears, and the ability to turn the hind flippers back under the body so that they can still function (if somewhat awkwardly) as feet when moving on land. I have seen Australian sea lions on coastal islands near Perth (there are boat tours that will take you to see them) and I can confirm that they can run along the beach at a surprising speed when they wish to. True seals have the hind flippers permanently directed behind them and so are forced to awkwardly belly-flop along when not swimming (doubtless as a result of this, true seals also differ from eared seals in that males lack an external scrotum). In the water, the hind flippers provide the main source of propulsion in true seals whereas eared seals get more of their thrust from the fore flippers (sea lions have been said to swim like penguins). As an aside, eared seals are also apparently unusual among mammals in that their milk completely lacks lactose. The lactose intolerant among you need not be denied dairy, you need only milk a walrus.

Mounted skeleton of Allodesmus sp., copyright Momotarou2012.


The earliest eared seals are known from the Miocene when they appear to have originated in the northern Pacific. Two extinct families from this place and period, the Enaliarctidae and Desmatophocidae, are commonly included in the Otarioidea, though it remains possible that either of these families should be placed outside the pinniped crown group, or closer to the true seals. The early Miocene Enaliarctidae differ from other otarioids in retaining differentiated premolars and molars (later forms have the cheek teeth uniform in appearance) and may well represent the ancestral form of the group. The mid- to late Miocene Desmatophocidae combined a rather Phocidae-like skull with a more Otarioidea-like post-cranium; the best-known genus Allodesmus had larger eyes than other otarioids and may have hunted in deep waters. One species of desmatophocid, Allodesmus sinanoensis, may have reached a length approaching five metres, making it larger than a modern walrus and rivalling the elephant seals in size. I highly recommend a series of posts on Allodesmus written a few years back by Robert Boessenecker (1, 2, 3, 4) that cover just about everything you might want to know about this animal.

Skull of Gomphotaria pugnax, from Robert Boessenecker.


Though only one walrus species is generally recognised in the modern fauna, the family was much more diverse in the past. However, most fossil Odobenidae lacked the tusks of a modern walrus and would have been more similar at a glance to sea lions. These early odobenids would have probably been generalist fish-feeders (Boessenecker & Churchill 2013). The modern walrus, in contrast, feeds primarily on bivalves. They don't crush the clam's shell but grab it with their lips and then suck powerfully enough that the meat is ripped out. Other than the tusks, the teeth of a modern walrus are small and weak; one close fossil relative, the Pliocene Valenictus chulavistensis, went so far as to lose the non-tusk teeth entirely. The tusks themselves are usually thought to function in display and the like rather than having any prominent role in feeding. However, it is an intriguing detail that the fossil whale Odobenocetops that converged in its feeding biology with walruses also possessed a large tusk. The non-tusk teeth were still used in feeding in the fossil clam-feeding walrus genera Dusignathus and Gomphotaria, which had a pair of large forward-directed tusks in both the upper and lower jaws.

Suckling South African fur seals Arctocephalus pusillus, copyright Robur.q.


The majority of living eared seals belong to the Otariidae, which have been divided in the past between the fur seals and sea lions. Fur seals tend to be smaller than sea lions and possess a dense layer of underfur. However, more recent phylogenetic studies (particularly molecular ones) have thrown this distinction out the window (e.g. Higdon et al. 2007). Instead, the northern fur seal Callorhinus ursinus of the north Pacific is probably the sister species to all other living otariids. Even the southern fur seals, generally placed in a single genus Arctocephalus, may not be monophyletic relative to the New Zealand sea lion Phocarctos hookeri (as a result, some authors have suggested resurrecting the genus Arctophoca for all southern fur seals other than the South African fur seal Arctocephalus pusillus). The South American fur seal Otaria flavescens may also be associated with this latter group. The two north Pacific sea lions, Steller's sea lion Eumetopias jubatus and the Californian sea lion Zalophus californianus, form a clade outside the southern otariids. The remaining species is the Australian sea lion Neophoca cinerea whose position has been harder to pin down: some analyses place it close to the New Zealand sea lion but others position it well away from all other southern otariids, possibly even outside all other otariids except the northern fur seal.

Walruses Odobenus rosmarus crowded on shore, from here.


Fur seals and sea lions were heavily hunted in the past for pelts and oil and some species remain endangered. Climate change poses a particular threat to cold-water species; for instance, recent years have seen significant contractions in walrus ranges, leading to dramatic crowding in the locations remaining. Conversely, the Antarctic fur seal Arctocephalus gazella, once feared extinct, has apparently exhibited a population explosion in recent decades, perhaps because lowered whale populations have led to more food being available for seals.

REFERENCES

Boessenecker, R. W., & M. Churchill. 2013. A reevaluation of the morphology, paleoecology, and phylogenetic relationships of the enigmatic walrus Pelagiarctos. PLoS One 8 (1): e54311.

Higdon, J. W., O. R. P. Bininda-Emonds, R. M. D. Beck & S. H. Ferguson. 2007. Phylogeny and divergence of the pinnipeds (Carnivora: Mammalia) assessed using a multigene dataset. BMC Evolutionary Biology 7: 216.

Repenning, C. A., & R. H. Tedford. 1977. Otarioid seals of the Neogene. Geological Society Professional Paper 992: i–vi, 1–93, 24 pls.

Turridae

Shell of Turris crispa crispa, copyright H. Zell.


At this point, I've made numerous references on this site to the gastropod family Turridae, discussing its members and non-members and alluding to its sordid history. So maybe I should set out the basics of the story properly.

The Conoidea are a diverse group of marine predatory gastropods with over 4000 known living species. They are best known for the production by many species of venom used to paralyse their prey, in some species being potent enought to threaten humans. In the majority of conoideans, this venom is delivered via a tooth that becomes detached from the radula and is held at the end of the retractable proboscis. Until relatively recently, Conoidea were commonly divided between three families. Two of these families, the Conidae (cone shells) and Terebridae (awl shells) were well defined and constrained. The third family was the Turridae, including by far the greater number of species but not really defined within Conoidea beyond 'the rest'. Many of 'the rest' were small, many were restricted to deep water, many were poorly known. Different systems were proposed over the years in an attempt to break the turrid mass into more manageable units but each system differed significantly from the next and no one system became universally accepted. Some authors would focus on the protoconch as their guide to classification, others would focus on the radula, others might call out features of the operculum. One author commented in 1922 that turrids were "considered by those who meddle with them to be more perplexing than any other molluscan family", and this complaint was still being upheld by Kilburn (1983) over sixty years later.

Though it had long been accepted that the 'turrids' probably did not represent an evolutionarily coherent group, it wasn't really until the advent of molecular phylogenies that things started falling into place. Puillandre et al. (2011) identified two main lineages within the Conoidea, leading to the dissolution of the original Turridae into no less than 13 families in order to maintain the already-established Conidae and Terebridae. Turridae in the strict sense was restricted to a much smaller clade of a bit over a dozen genera, sister to the Terebridae (Bouchet et al. 2011).

In contrast to the bewilderment of the original turrid array, Turridae sensu Bouchet et al. is a morphologically quite coherent group. They are more or less fusiform (spindle-shaped) shells, often with a narrow, high spire and relatively weak sculpture. Indeed, but for the fact that most tend to have a long siphonal canal at the base of the shell, they often bear a distinct resemblance to their sister group, the terebrids. The majority of turrids have a multispiral protoconch, indicating an extended, planktonic-feeding larval stage in development, but there are some species with a paucispiral protoconch indicative of direct development.

Radula of Xenuroturris legitima, from Kantor & Puillandre (2012); ct = central tooth.


The radula of turrids usually comprises three apparent teeth in each row. The central tooth is actually formed from three teeth (the original pointed central tooth and two plate-like lateral teeth) fused together; in some species the division between these teeth remains visible whereas in others the central tooth disappears entirely. The main business part of the radula is the single pair of marginal teeth which, as in other conoideans, are enlarged and modified for venom delivery. They have a distinctive 'duplex' form; in older publications, this was referred to as a 'wishbone' form because the tooth appears under light microscopy to be divided between two branches. After the advent of electron microscopy, it was discovered that these two 'branches' in fact represent the thickened margins of an undivided tooth. The larger of the two margins is mostly attached to the radular membrane with only the tip of the tooth being free; the smaller margin is held free of the radula. The thinner part of the tooth between the two margins forms a gutter along which venom can flow. However, the radula is placed in such a position that it cannot be protruded through the mouth in the manner of grazing gastropods. As with other conoideans, prey (in this case probably worms) is despatched through the use of a detached marginal tooth transferred to the end of the proboscis. However, whereas other conoideans such as cone shells may have the tooth functioning like a hypodermic syringe for delivering prey, turrids use their tooth to slash at the prey like a switchblade, with venom passively entering through the resulting cuts. The proboscis is then used to draw the prey back into the mouth, where the radula is used to grasp and swallow it, sucking the unlucky worm down the gullet like spaghetti.

REFERENCES

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

Kantor, Y. I., & N. Puillandre. 2012. Evolution of the radular apparatus in Conoidea (Gastropoda: Neogastropoda) as inferred from a molecular phylogeny. Malacologia 55 (1): 55–90.

Kilburn, R. N. 1983. Turridae (Mollusca: Gastropoda) of southern Africa and Mozambique. Part 1. Subfamily Turrinae. Annals of the Natal Museum 25 (2): 549–585.

Puillandre, N., Y. I. Kantor, A. Sysoev, A. Couloux, C. Meyer, T. Rawlings, J. A. Todd & P. Bouchet. 2011. The dragon tamed? A molecular phylogeny of the Conoidea (Gastropoda). Journal of Molluscan Studies 77: 259–272.

Blister Beetles

Zonitis sayi, copyright Carol Davis.


This is a blister beetle of the genus Zonitis. Blister beetles, the family Meloidae, get their name from their production of cantharidin, a defensive chemical that can burn the skin of would-be predators. Zonitis is a widespread genus of blister beetles with over 100 species described from around the world. However, it should be noted that its wide distribution may relate to the genus being poorly defined and future revisions may divide its members between other genera (as I believe has already happened for the Australasian 'Zonitis'). As it is, Zonitis species are characterised by fully developed elytra and functional wings, and cleft tarsal claws with two rows of teeth on the upper section (Enns 1956). Adult Zonitis are flower-feeders, visiting composite plants (i.e. daisies and similar plants), and some species have the mouthparts modified into a tube for sucking nectar.

Most blister beetles exhibit what is known as hypermetamorphism or hypermetaboly, where the larvae pass through morphologically differentiated stages before reaching pupation. Zonitis species develop as parasitoids or kleptoparasites of bees. Females lay large numbers of eggs (up to and exceeding 500 in a batch) on their host plant, most commonly on the flowers though sometimes on the undersides of leaves. The eggs hatch into active, long-legged larvae that attach to bees visiting the flowers and so get carried to the bee's nest. Once there, they moult into a less mobile stage and feed on the food stores laid aside for the bee's larva, and potentially on the larva itself. In the North American species Zonitis atripennis flavida, the beetle larva completes its development in a single cell but European species consume the contents of two bee cells before reaching maturity. Following the initial active instar, meloid larvae pass through four feeding instars before entering a quiescent, immobile stage called the hypnotheca or prepupa. The hypnotheca moults into another feeding instar before the larva finally enters the pupal stage (Bologna et al. 2008). What the point (if anything) of the hypnotheca is, I have no idea. However, it is worth noting that hypnothecae of another meloid species, Hornia boharti, have been recorded surviving for multiple years without feeding before moulting to the next instar.

Once adults emerge from the host cell, they of course disperse to conduct their own affairs. Natural history data is patchy but indications are that many species are picky in their choice of host plant. From an economic perspective, their damaging role as a parasite of pollinating bees may be partially counterbalanced by their potential role as pollinators in their own right, but who can say which way the scales lean?

REFERENCES

Bologna, M. A., M. Oliverio, M. Pitzalis & P. Mariottini. 2008. Phylogeny and evolutionary history of the blister beetles (Coleoptera, Meloidae). Molecular Phylogenetics and Evolution 48: 679–693.

Enns, W. R. 1956. A revision of the genera Nemognatha, Zonitis, and Pseudozonitis (Coleoptera, Meloidae) in America north of Mexico, with a proposed new genus. University of Kansas Science Bulletin 37 (2): 685–909.

Cicadomorpha

Textbooks will tell you that the term 'bug' should be restricted to insects of the order Hemiptera though, as I've noted before, I don't know if I've ever met anyone who actually used the word that way. For many people, one of the groups of actual bugs that they are most likely to be aware of are members of the Cicadomorpha.

Tasmanian hairy cicada Tettigarcta tomentosa, copyright Simon Grove.


Cicadomorphs include the cicadas (Cicadoidea), leafhoppers (Membracoidea) and spittlebugs (Cercopoidea). As a group, they are distinguished by an enlarged postclypeus (the upper part of the front of the head below the antennae), simple antennae with a whip-like flagellum, and small and narrowly placed mid-coxae (Dietrich 2005). The enlarged postclypeus is associated with adaptations for feeding on xylem, deeper in the plant stem than many other plant-sucking bugs prefer, though derived subgroups of the leafhoppers have changed back to phloem or parenchyma. Well over 30,000 species of cicadomorph are known from around the world. Cicadas can be readily distinguished from other cicadomorphs by their possession of three ocelli in a triangle on the top of the head whereas leafhoppers and spittlebugs have only two or no ocelli.

Male bladder cicada Cystosoma saundersii, one of the world's more ridiculous animals, from Brisbane Insects.


Cicadas are best known, of course, for their singing. The songs are produced by a pair of membranous 'drums', the tymbals, at the base of the abdomen; muscular vibration of the membranes produces the sound. In most cicadas, only the male possesses these tymbals. However, both sexes possess tymbals in the hairy cicadas Tettigarcta, two species found in alpine regions in south-eastern Australia. Hairy cicadas also differ from the remaining cicadas in other ways, most notably in lacking the well-developed tympana on the underside of the abdomen that typical cicadas hear with (hairy cicadas have simpler hearing organs in their place). As a result, Tettigarcta is placed in its own distinct family, sister group to the remaining cicadas in the Cicadidae. Though now restricted to Australia, fossil species from the Mesozoic and Palaeogene of other parts of the world have also been placed in the Tettigarctidae (Shcherbakov 2008); however, they are mostly so placed on the basis of shared primitive rather than derived features and may well represent stem taxa for Cicadoidea as a whole. Other derived features of the cicadas proper in the Cicadidae include gas-filled chambers in the abdomen that resonate the calls produced by the tymbals. In males of another Australian species, the bladder cicada Cystosoma saundersii, these resonating chambers reach a remarkable size and the entire abdomen looks to have been blown up like a beach ball.

Froghopper Cercopis vulnerata, copyright Richard Bartz.


The spittlebugs or froghoppers of the Cercopoidea are smaller cicadomorphs, distinguished from species of the Membracoidea by their short and cylindrical (rather than long and quadrate) hind tibiae. The name 'spittlebug' refers to the nymphs of these bugs living covered with a protective covering of foam. In one family, the Machaerotidae, the nymph produces a calcareous tube around itself that it fills with fluid. The foam or fluid used for protection by cercopoids is primarily composed of the nymph's own excrement: the xylem fluids that they feed on are mostly water, after all, so they produce a large quantity of watery excreta.

Mango leafhopper Idioscopus nagpurensis, one of the world's many, many species of Cicadellidae, copyright Arian Suresh.


The third main subgroup of the cicadomorphs, the Membracoidea, is by far the most diverse, particularly the largest family Cicadellidae (leafhoppers). My own impression from my experience of collecting insects in various locations is that cicadellids are just everywhere. Over 20,000 species of this family have been described to date, and it has been estimated that the true number may be much higher. For instance, at one location in North America close to 100 species of a single genus Erythroneura have been recorded from a single plant (Dietrich 2002). Just how such a high diversity of closely related species can live in such close proximity remains a largely unanswered question, though some studies have apparently suggested the possibility of very fine micro-habitat partitions (making sense of the great mass of cicadellid diversity is not helped by many species exhibiting dimorphism between flying and flightless forms, similar to that I recently described for delphacids). Another notable feature of cicadellids is the protection of brochosomes, tiny, hollow, soccerball-like granules constructed of protein nets with which the leafhopper coats itself after moulting. The hydrophobic brochosomes help to keep the hopper free of water droplets and its own wet, sticky excreta. They may also serve other protective functions: females will coat newly laid eggs with a layer of brochosomes that may serve to prevent egg parasitoids such as micro-wasps from attacking the eggs.

Membracid leafhopper Cladonota benitzei, copyright P. Lahmann.


The membracoids also include the Membracidae, renowned for the remarkable appearance of the pronotal shield (the top and front of the thorax) in many species. In more humble membracids, the pronotum may form a high mound or pillar, but in others it may extend into bizarre arrangements of globules and branched spines hanging above the leafhopper like a baroque chandelier. Again, just what the purpose of this extravagant morphology is remains unknown but many authors have proposed some sort of protective function. It has been suggested that pronotal projections may help membracids mimic part of their host plant, or potential predators such as parasitic wasps. Alternatively, they mean that potential predators such as birds find the hopper just too hard to swallow.

REFERENCES

Dietrich, C. H. 2002. Evolution of Cicadomorpha (Insecta, Hemiptera). Denisia, Neue Folge 4 (176): 155–170.

Dietrich, C. H. 2005. Keys to the families of Cicadomorpha and subfamilies and tribes of Cicadellidae (Hemiptera: Auchenorrhyncha). Florida Entomologist 88 (4): 502–517.

Shcherbakov, D. E. 2008. Review of the fossil and extant genera of the cicada family Tettigarctidae (Hemiptera: Cicadoidea). Russian Entomological Journal 17 (4): 343–348.

The Colours of Rot

Bracket fungi Fomitopsis pinicola, copyright Marek Novotnak.


Apart from those species readily purchased at the supermarket, perhaps the macrofungi most likely to be encountered by the average person are the brackets. Bracket fungi are the hard, woody, shelf-like fungi that may be found growing from tree-stumps and fallen logs. Whereas other fungal fruiting bodies may emerge, release their spores, and collapse away within a matter of hours, those produced by bracket fungi (properly known as 'conks', apparently) may persist for years with a new layer of reproductive tissue added each cycle.

Phlebiopsis gigantea, a resupinate member of the Polyporales, copyright Jerzy Opioła.


The majority of brackets belong to the fungal order Polyporales, one of the major subgroups of the basidiomycetes with about 1800 known species (Binder et al. 2013). While brackets may be the most familiar Polyporales, the order is morphologically diverse. Indeed, no one morphological feature characterises the Polyporales as currently recognised; it has only been recognised as a clade following the advent of molecular analyses. Some members of the Polyporales produce persistent fruiting bodies like brackets, others are more ephemeral. They may be sessile and shelf-like, or they may be raised on a stalk. The spore-producing layer may appear as minute pores, as gills, as protruding teeth, or may be entirely smooth. There are also a large number of Polyporales species that are what is known as resupinate: that is, they don't produce discrete fruiting bodies at all. Instead, the reproductive structures are produced as a more or less undifferentiated crust spreading over their substrate.

Hexagonal-pored polypore Polyporus alveolaris, copyright Andreas Kunze.


The greater number of Polyporales are associated with decaying wood; they play an integral role in breaking down and releasing nutrients that might otherwise be locked away from environmental cycles. Most species only grow on wood that is already deceased but there are some that are pathogenic on living trees. Based on the appearance of the wood being broken down, Polyporales may be divided between 'white-rot' and 'brown-rot' species. The difference is not merely an aesthetic one. Wood is made up primarily of two organic polymers, cellulose and lignin. Both these chemicals are difficult to metabolise (we ourselves, for instance, cannot digest either) but lignin is a particularly tough nut to crack. White-rot fungi are able to digest both cellulose and lignin but brown-rot fungi digest the cellulose only. White-rot fungi extract more nutrients from the wood overall but brown-rot fungi extract nutrients faster. And while the efforts of white-rot fungi may result in almost the entire carbon quotient of the wood being released to the environment, brown-rot fungi leave a lignin-rich residue that is largely indigestable by any other organism. Genomes have been sequenced from both white- and brown-rot taxa and a fair amount of effort has been invested into studying the different chemical pathways underlying the different rot types.

Caulifower fungus Sparassis brevipes, copyright AL'S.


Phylogenetically speaking, Justo et al. (2017) recently recognised eighteen families within Polyporales corresponding to well-established molecular clades (plus a handful of taxa that could not yet be confidently placed in a 'family') but these show the same challenges to morphological characterisation as the order as a whole. Many of these families include both fruiting and resupinate taxa, and transitions in fruiting body morphology are the rule more than the exception. Interestingly, one 'morphological' feature that does show a fair degree of phylogenetic consistency is the rot-type. It seems clear that the ancestor of the Polyporales was a white-rot fungus with the majority of brown-rot fungi forming a single clade within the order. Only one known brown-rot fungus genus , Lentiporus, definitely evolved separately from the rest (another genus, Auriporia, may or may not represent a further origin of brown rot). One question that remains to be answered is whether the chemical basis of brown rot in Laetiporus is the same as that in the main brown-rot clade.

Ganoderma pfeifferi, copyright Bloodworm.


Apart from their role in breaking down wood, not too many Polyporales have a direct economic significance. Some, notably the lingzhi Ganoderma lucidum, are grown commercially for use in Chinese medicine. Some species with more fleshy fruiting bodies are edible: notable examples include the cauliflower fungi Sparassis species and the chicken of the woods Laetiporus sulphureus (guess what it's supposed to taste like). According to its Wikipedia page, chicken of the woods may cause a toxic reaction to some diners but there seems to be some question about whether this is due to toxins produced by the fungus itself or whether the fungus is absorbing toxins contained in the wood it is growing from. For other polypores, the question of toxicity may be rendered moot by the fact that any attempt to eat one would break one's teeth.

REFERENCES

Binder, M., A. Justo, R. Riley, A. Salamov, F. Lopez-Giraldez, E. Sjökvist, A. Copeland, B. Foster, H. Sun, E. Larsson, K.-H. Larsson, J. Townsend, I. V. Grigoriev & D. S. Hibbett. 2013. Phylogenetic and phylogenomic overview of the Polyporales. Mycologia 105 (6): 1350–1373.

Justo, A., O. Miettinen, D. Floudas, B. Ortiz-Santana, E. Sjökvist, D. Lindner, K. Nakasone, T. Niemelä, K.-H. Larsson, L. Ryvarden & D. S. Hibbett. 2017. A revised family-level classification of the Polyporales (Basidiomycota). Fungal Biology 121: 798–824.

Meandering Forams

Specimen of Meandropsina vidali, showing the patterning on the external surface, from Loeblich & Tappan (1964).


There are some taxonomic names that just instantly bring up a mental image of the sort of organism to which they refer. For my part, I've always felt that Meandropsina is one of those names. The Meandropsinidae are another family of relatively large and complex foraminifera (growing up to a number of millimetres across) that are known only from the Upper Cretaceous. The several genera of the family are predominantly European, with only the genus Fallotia also known from the West Indies.

Cross-section of Meandropsina vidali, from Loeblich & Tappan (1964).


Meandropsinids are (as far as I know) more or less lenticular in shape with chambers enrolled in a flat spiral. The name of the type genus Meandropsina refers to the way that the outer margins of the chambers tend to meander irregularly around the test, giving it something of an ornate appearance. Both molecular and structural evidence indicate that multi-chambered forams arose from ancestors with undivided tests on more than one occasion, and the majority of multi-chambered forams can be assigned to two major lineages (Pawlowski et al. 2013). In one lineage, the Globothalamea (which includes, for instance, the rotaliids), the basic chamber shape is globular with successive chambers in the test being wider than long. In the other lineage, the Tubothalamea (including the miliolids and spirillinids), the basic chamber shape is tubular, and the test may grow through a number of spirals before it even starts to be divided into chambers (if at all). Members of the two lineages with calcareous tests may also be distinguished by their test structure: in calcareous globothalameans, the crystals making up the test are arranged regularly so the overall appearance of the test is hyaline (glass-like). In contrast, tubothalameans have the crystals of the test arranged irregularly so the appearance of the test is porcelaneous (like porcelain). Meandropsinids are unmistakeably tubothalameans in both regards.

Like other large forams of the Mesozoic, meandropsinids did not make it past the end of the Cretaceous. Early Palaeocene taxa that have been included in the families represent distinct lineages that evolved to take their place, occupying the ecological spaces opened up by the mass extinction ending the era.

REFERENCES

Loeblich, A. R., Jr, & H. Tappan. 1964. Treatise on Invertebrate Paleontology pt C. Protista 2. Sarcodina: chiefly "thecamoebians" and Foraminiferida vol. 1. The Geological Society of America, and The University of Kansas Press.

Pawlowski, J., M. Holzmann & J. Tyszka. 2013. New supraordinal classification of Foraminifera: molecules meet morphology. Marine Micropalaeontology 100: 1–10.

Doe, it's Deer

Marsh deer Blastocerus dichotomus, copyright Jonathan Wilkins. An animal that just screams out, "Am I wearing the Chanel boots? Yes, I am."


I hardly need to explain what deer are, do I? Deers (Cervidae) are generally recognised as the second most diverse family of hoofed mammals (after bovids) in the modern fauna. Their most recognisable feature, of course, is the possession of antlers: bony cranial appendages that are shed and regrown every year rather than being permanently in place like the horns of a bovid. When antlers first grow, they are covered with a layer of skin (the velvet) that supplies them with blood, but this skin is later shed to expose the bare bone. In most species, antlers are only grown by males whose use them in conflicts during the mating season. The only genus of deer that grows antlers in both sexes is Rangifer, the reindeer. There is also one living species that lacks antlers, the Chinese water deer Hydropotes inermis; instead of antlers, males of this species possess large, dagger-like canines. In the majority of deer species, antlers are subcylindrical and often branched but broad palmate antlers have evolved on multiple occasions within the family. Antler morphology is generally significant in distinguishing taxa but it should be noted that variation within species is not unknown. For instance, the few recorded males of the small, now possibly extinct population of moose introduced to the south of New Zealand lacked the large palmate antlers generally associated with the species, probably due to poor nutritional conditions. Instead, they had more slender antlers that only became moderately palmate distally, like those of a fallow deer Dama dama.

One of the few photographs of moose from New Zealand, from here. I think this might be the one shot at Herrick Creek in 1952 but I could be wrong.


The first antlered deer are known from Europe back in the early Miocene, about 17 million years ago. They are not known from North America until some time later in the Pliocene, about five mya (Pitra et al. 2004), though these days they are every bit as diverse in the Americas as in Eurasia. They never made much inroad into Africa, only extending into the northernmost part of the continent, and they never made it into Australasia under their own steam, though a number of species have been dispersed to various parts of the world by humans. For instance, at least half a dozen species have become established in New Zealand, and until recently reindeer might be found wandering among penguin colonies in South Georgia.

Reindeer and king penguins on South Georgia, from here.


Recent decades have seen some pretty wild swings in cervid taxonomy, with the number of subfamilies recognised varying from two to seven, and some authors recognising a much larger number of genera and species than others. However, our general understanding of cervid interrelationships is pretty good these days, with many differences between systems being a question of ranking more than anything else. Recent studies have agreed that modern deer can be divided between two primary lineages that may be called the Cervinae and Capreolinae (Gilbert et al. 2006). The Cervinae include the majority of deer species in the Old World with a single species (the wapiti Cervus canadensis) extending its range into the New World. The remaining New World deer all belong to the Capreolinae, which also includes four genera (Rangifer, Hydropotes, the roe deer Capreolus and the moose Alces) found in Eurasia.

Male tufted deer Elaphodus cephalophus, copyright Heush.


The Cervinae can be divided between two tribes, the Muntiacini and Cervini. Muntiacini include the muntjaks of the genus Muntiacus and the tufted deer Elaphodus cephalophus. These are small deer native to southern and eastern Asia. Antlers are small and simple in all Muntiacini: muntjaks have antlers with only a single short anterior branch whereas the tufted deer has unbranched antlers that are barely visible under the large tuft of hair that this species has on top of the head. Muntiacini also resemble Hydropotes in their possession of large canines in the males. The other tribe, Cervini, includes larger deer species with more complex, multi-branched antlers. Some authors have historically placed all species of Cervini within a single genus Cervus; others may recognise nine distinct genera. Numbers of recognised species have also varied, largely due to phylogenetic studies finding that taxa previously recognised as conspecific subspecies may be more distantly related to each other or may not form monophyletic units. For instance, the wapiti has often been regarded as a subspecies of the red deer Cervus elaphus but recent studies have suggested that it is more closely related to the sika C. nippon and the white-lipped deer Przewalskium or Cervus albirostris, two east Asian species (Pitra et al. 2004). Difficulties in elucidating cervin phylogeny are probably best exemplified by the case of Père David's deer Elaphurus or Cervus davidianus, originally native to southern China but now only surviving in captivity. Molecular phylogenies associate this species closely with the brow-antlered deer Cervus eldi but it has many morphological features indicating a close relationship with C. elaphus, and it is widely suspected that Père David's deer originated from a hybridisation event between the two latter species.

Pudu (I think a northern pudu Pudu puda), copyright Neil McIntosh.


The Capreolinae can be divided between three main lineages. One comprises the roe deer and water deer; another comprises the moose (again, I'm making a point of referring to genera rather than species because the number of recognised species may differ between authors). Note that the position of the water deer suggests that the antler-less state of this species represents a secondary loss rather than retention of a primitive state. The majority of capreolines belong to the third lineage, commonly recognised as the tribe Odocoileini. Except for the reindeer, the species of this lineage are restricted to the New World, with the higher diversity in South America. The Odocoileini are perhaps the most taxonomically uncertain section of the deer family. There appears to be no question, at least, that Rangifer represents the sister group of all other Odocoileini. The remaining odocoileins have generally been divided between six genera: Odocoileus (including the mule deer O. hemionus and white-tailed deer O. virginianus), Mazama (brockets), Pudu (pudus), Hippocamelus (guemuls), the marsh deer Blastocerus dichotomus and the pampas deer Ozotoceros bezoarticus. However, except for the two monotypic genera, monophyly of all these taxa was placed in question by a recent molecular phylogenetic study of the group by Gutiérrez et al. (2017). The issue is particularly marked for the brockets, small deer with unbranched antlers, as not only the genus as a whole but also species within the genus have been indicated as non-monophyletic. Recent years have, as a result, seen something of a burst of new brocket species being described. It is quite probable that a similar taxonomic explosion may be in line for the genus Odocoileus, with both of the currently recognised species including a number of subspecies and each being of suspect monophyly. Matters are further complicated by the possibility of hybridisation between the two 'species'.

REFERENCES

Gilbert, C., A. Ropiquet & A. Hassanin. 2006. Mitochondrial and nuclear phylogenies of Cervidae (Mammalia, Ruminantia): systematics, morphology, and biogeography. Molecular Phylogenetics and Evolution 40 (1): 101–117.

Pitra, C., J. Fickel, E. Meijaard & P. C. Groves. 2004. Evolution and phylogeny of Old World deer. Molecular Phylogenetics and Evolution 33: 880–895.