I’ve said a few times here at TetZoo that bats have never really been given adequate coverage. This isn’t because I’m not interested in them: on the contrary, I think about bats more than I think about most other groups of mammals, and I see them and watch them more often than I do most other mammal groups. For a group that includes about 18% of extant mammalian species (using 2019 figures*), I can’t pretend to have ever given bats fair coverage. Having said all that, bats have actually been covered at TetZoo a fair bit: there was an entire 20-part series on vesper bats (properly Vespertilionidae) at ver 3, and I also published several ver 2 articles on the history and evolution of vampire bats, and on much else besides. The fact that all of these articles have been rendered worthless via the removal of their images is mightily dispiriting though, and essentially means that I need to start from scratch.
* c 6495 mammal species, c 1200 bat species.
Here, I want to talk about a group I don’t think I’ve ever covered at TetZoo before, namely the phyllostomids, or New World leaf-nosed bats, American leaf-nosed bats or spear-nosed bats. This is a large, American group that contains around 200 living species, making it the third largest bat family (vesper bats are the biggest group, followed by fruit bats). The group has sometimes been called Phyllostomatidae – the vernacular version of which is phyllostomatid – but this is less popular than Phyllostomidae. I have no idea which is really correct here and opt to merely follow majority usage on these sorts of things (insert quote from Gene Gaffney**). It’s not strictly true that I’ve never covered phyllostomids before, since vampires – once upon a time given their own eponymous family (Desmodontidae) – are now universally agreed to be nested within Phyllostomidae, and I have at least written about them.
Phyllostomids occur from Argentina in the south to the southern USA (Nevada being their most northerly occurrence) in the north, and they’re highly diverse ecologically and behaviourally. They include insectivores, frugivores, nectarivores, palynivores (that’s pollen-eaters), omnivores, animalivores and (of course) obligate sanguivores. Numerous different taxonomic subdivisions have been named. We don’t need to worry about any of this in detail but, in simplified terms, Macrotinae (big-eared bats), Micronycterinae (little big-eared bats) and Desmodontinae (vampires) are outside a much larger clade that includes Vampyrinae (false vampires and kin) and Phyllostominae (spear-nosed bats and kin) as well as the nectarivorous and frugivorous Glossophaginae (long-tongued and long-nosed bats) and Stenodermatinae (American fruit bats, fig-eating bats and kin) (Baker et al. 1989, 2003, 2012; but see Wetterer et al. 2000). Vampyrinae is a clade within Phyllostominae according to some studies, in which case it gets down-graded to Vampyrini (Baker et al. 2003). All of this is depicted in a cladogram below.
Phyllostomids are mostly brownish bats with simple, narrow ears. A nose-leaf – typically simple and spear-shaped – is common but not present in all species, a tragus is always present, and the species that lack nose-leaves have chin-leaves (or a series of chin ‘warts’) instead. Facial stripes are common, dark dorsal stripes are present in a few species, and such things as white patches at the wing tips and yellow rims to the ears and nose-leaves are present in some (Hill & Smith 1984). The tail is variously long, or short, and even absent altogether in some taxa, and similar variation is present in the uropatagium, or tail membrane.
Skeletally, phyllostomids are robust, have a distinctive humerus where the distal end is angled relative to the shaft, and have a prominent secondary articulation between the large bony lump (properly termed the greater tuberosity) at the proximal end of the humerus and the scapula (Czaplewski et al. 2007). That’s right: a number of bat groups have an accessory peg-in-socket articulation involving the humerus and the body of the scapula. This means that the humerus and scapula are locked together during the upper part of the wing stroke (Hill & Smith 1984).
Some phyllostomids are really exceptional as goes their anatomical and behavioural novelty. Perhaps the most remarkable are the long-tongued glossophagine flower bats, some of which have extraordinary tubular snouts, remarkably long tongues tipped with papillae, and a highly reduced dentition. The most extreme example of this sort of thing is the Banana bat, Trumpet-nosed bat or Colima long-nosed bat Musonycteris harrisoni of Mexico, an ‘extreme’ mammal as goes snout length. It’s fairly typical for people who aren’t that familiar with bat diversity to confuse glossophagines with the Old World flower-feeding megabats grouped together in Macroglossinae. There’s obviously a degree of evolutionary convergence here, though it hasn’t been that well explored in the literature, to my knowledge. Various glossophagines have symbiotic relationships with sympatric plants. Incidentally, Pallas’s long-tongued bat Glossophaga soricina is able to see UV light (Winter et al. 2003).
Entirely different specialisations are seen in the short-faced, frugivorous phyllostomids included within Stenodermatinae. These have flattened, broad teeth, typically have white facial stripes (an aposematic warning of their powerful bites?), and are sometimes handsome or even cute, big-eyed bats. One of the strangest of bats – the Wrinkle-faced or Lattice-winged bat Centurio senex – belongs to this group. The naked, wrinkled faces of males are mostly concealed by massive skin flaps when the bat is roosting or sleeping. There are also neck glands that seem to secrete scent, and obvious transverse bands on the wing membranes.
My favourite phyllostomids are very different from tubular-snouted flower-feeders and short-face fruit-eaters: they are the robust, more generalised species traditionally lumped together in Phyllostominae (though the name Vampyrinae has also been used for some of them). These are mostly omnivores that eat insects, fruit and small vertebrates, and some are specialised predator bats that variously catch and eat amphibians, mammals (including other bats) and birds. They include Peters’s woolly false vampire Chrotopterus auritus, the Frog-eating bat Trachops cirrhosus – famous for eating frogs and selecting them on the basis of their calls – and the spectacular Linnaeus’s false vampire Vampyrum spectrum, a predatory giant that can, in cases, have a wingspan of over 1 meter.
When this variation in feeding ecology is mapped onto a phylogeny, it would appear that the earliest phyllostomids were insectivorous, that omnivory, nectarivory (or nectivory, take your pick) and palynivory evolved from among these insectivores, and that frugivores evolved from among nectarivores and palynivores (Baker et al. 2012). The highly specialised vampires appear – according to phylogenetic data – to have evolved directly from insectivores (which is a surprise in view of some models proposed to explain vampire evolution) and at least some members of the main frugivorous clade appear to have reverted to insectivory (Baker et al. 2012; but see Wetterer et al. 2000). Of the various evolutionary events that must have occurred here, it’s the transition to obligate frugivory that seems to have been the most successful, since the frugivorous clade is the largest (as in, most species-rich) within Phyllostomidae, containing about 70 species in 20 genera.
This is also the radiation that’s seemingly resulted in the greatest, most rapidly evolved amount of morphological variation, since everything here seems to have happened within the last 10 million years and has given rise to taxa that are among the most divergent and specialised of phyllostomids. Also of interest here is that the frugivorous clade appears to have evolved in the Antilles before invading the mainland (Dávalos 2007), a case of ‘upstream colonisation’ that contradicts traditional scenarios whereby continental animals give rise (via ‘downstream colonisation’) to island-dwelling forms.
Where in the bat tree? What sort of bats are phyllostomids, and what do we know about their evolutionary history? On the basis of anatomical characters, bat experts have generally thought that phyllostomids are close allies of naked-backed, moustached or ghost-faced bats (Mormoopidae) and bulldog bats and kin (Noctilionidae), the whole lot being grouped together in a clade termed either Phyllostomatoidea or Noctilionoidea (and it’s the last of those terms that should be preferred, so I understand). In turn, this group was thought – again, on the basis of anatomical characters – to be closely related both to vesper bats and their kin (Vespertilionoidea), and to a clade that includes both sheath-tailed bats and kin (Emballonuroidea) and horseshoe bats and kin (Rhinolophoidea) (Smith 1976).
Molecular studies, mostly published since 2000, have substantially revised our view of the bat family tree, however, and it’s now clear that rhinolophoids are not close to the other groups listed here at all (they are, instead, close relatives of megabats). Noctilionoids are still close kin of vespertilionoids, however. It also now seems that Mystacinidae and Myzopodidae are part of Noctilionoidea (Jones et al. 2002, 2005, Teeling et al. 2005, 2012). I’ll be talking more about ideas on bat phylogeny in a future article.
What does the fossil record say about phyllostomid history? The pre-Pleistocene phyllostomid record is not great but it’s still at least good enough to show that the extinct phyllostomids of the Miocene – most notably those from La Venta in Colombia – were superficially much like living ones, and that the extinct species concerned were doing the sorts of things that phyllostomids do today. The group had almost certainly, therefore, undergone its main flowering and diversification by around 20 million year ago. The Pleistocene phyllostomid record, in contrast, is good and numerous extant taxa are known from sediments of this age.
And that’s where we’ll end things for now. I’d like to say a lot more about these bats, so we’ll be returning to them in time. And in fact I need to say a lot more about bats in general, so stay tuned for that too.
If you enjoyed this article and want to see me do more, more often, please consider supporting me at patreon. The more funding I receive, the more time I’m able to devote to producing material for TetZoo and the more productive I can be on those long-overdue book projects. Thanks!
For previous TetZoo articles on bats (concentrating here on articles that haven’t been stripped of images, as is the case for all ver 2 articles and the vast majority of ver 3 articles)…
Chewed bones and bird-eating microbats, June 2006
We flightless primates (on the Pettigrew ‘megabats are close kin of primates’ model), August 2006
Fossil Bat Stories, Part 1, February 2018
Fossil Bat Stories, Part 3: Bulldog Bats, February 2018
Refs - -
Baker, R. J., Bininda-Emonds, O. R. P., Mantilla-Meluk, H., Porter, C. A. & Van Den Bussche, R. A. 2012. Molecular time scale of diversification of feeding strategy and morphology in New World leaf-nosed bats (Phyllostomidae): a phylogenetic perspective. In Gunnell, G. & Simmons, N. (eds). Evolutionary History of Bats: Fossils, Molecules and Morphology. Cambridge University Press, Cambridge, pp. 385-409.
Baker, R. J., Hoofer, S. R., Porter, C. A. & Van Den Bussche, R. A. 2003. Diversification among New World leaf-nosed bats: An evolutionary hypothesis and classification inferred from digenomic congruence of DNA sequence. Occasional Papers, Museum of Texas Tech University 230, 1-32.
Baker, R. J., Hood, C. S. & Honeycutt, R. L. 1989. Phylogenetic relationships and classification of the higher categories of the New World bat family Phyllostomidae. Systematic Zoology 38, 228-238.
Czaplewski, N. J. 1997. Chiroptera. In Kay, R. F., Madden, R. H., Cifelli, R. L. & Flynn, J. J. (eds) Vertebrate Paleontology in the Neotropics: The Miocene Fauna of La Venta, Colombia. Smithsonian Institution Press (Washington and London), pp. 410-431.
Dávalos, L. M. 2007. Short-faced bats (Phyllostomidae: Stenodermatinae): a Caribbean radiation of strict frugivores. Journal of Biogeography 34, 364-375.
Jones, K. E., Bininda-Emonds, O. R. P. & Gittleman, J. L. 2005. Bats, clocks, and rocks: diversification patterns in Chiroptera. Evolution 59, 2243-2255.
Jones, K. E., Purvis, A., MacLarnon, A., Bininda-Emonds, O. R. P. & Simmons, N. B. 2002. A phylogenetic supertree of the bats (Mammalia: Chiroptera). Biological Reviews 77, 223-259.
Smith, J. D. 1976. Chiropteran Evolution. Texas Tech University, Lubbock.
Teeling, E. C., Dool, S. & Springer, M. S. 2012. Phylogenies, fossils and functional genes: the evolution of echolocation in bats. In Gunnell, G. & Simmons, N. (eds). Evolutionary History of Bats: Fossils, Molecules and Morphology. Cambridge University Press, Cambridge, pp. 1-22.
Teeling, E. C., Springer, M. S., Madsen, O., Bates, P., O’Brien, P. & Murphy, W. J. 2005. A molecular phylogeny for bats illuminates biogeography and the fossil record. Science 307, 580-584.
Wetterer, A. L., Rockman, M. V. & Simmons, N. B. 2000. Phylogeny of phyllostomid bats (Mammalia: Chiroptera) data from diverse morphological systems, sex chromosomes, and restriction sites. Bulletin of the American Museum of Natural History 248, 1-200.
Winter, Y., López, J. & von Helversen, O. 2003. Ultraviolet vision in a bat. Nature 425, 612-614.
** In a technical article on fossil side-necked turtles, Gaffney said of a very similar nomenclatural disagreement: “it’s true, I don’t give a rat’s ass which is used”.