The ‘hedgehog’ tenrecs: they nest with hedgehogs

This is a think piece.
You’re going to be faced with

  1. a geographically inspired return of the cloaca (proposed heresy) or
  2. MASSIVE convergence involving everything but the cloaca (current and traditional paradigm)

Arguments will be presented.
You decide which is more parsimonious. We may need to bring in the DNA guys here, and I would welcome them! I don’t think such a study involving a wide range of purported and actual tenrecs has been proposed or done yet. Let me know as I am unaware of published work on this subject.

The present problem had its genesis in whale phylogenetic studies.
Earlier, from skeletal data, the the large reptile tree (LRT) nested odontocete (toothed) whales with tenrecs and mysticete (baleen) whales with hippos and desmostylians.

current DNA studies do not support the tenrec – odontocete relationship — perhaps because workers used the lesser hedgehog tenrec (Echinops telfairi, Martin 1838, Figs. 2, 3) in their DNA studies. Echinops is traditionally considered a tenrec, but it may not be one based on bones (Fig. 3) and massive homology/convergence with the European hedgehog, Erinaceus (Figs. 1, 3).

Figure 4. European hedgehog, a member of Glires.

Figure 1. European hedgehog, Erinaceus, a member of Glires.

It’s the cloaca that seems to matter most
in tenrec studies. Plus the location: Madagascar.

Figur3 5. Madagascar hedgehog, is not a tenrec, but another member of Glires.

Figure 2. Madagascar hedgehog tenrec, Echinops, perhaps not a tenrec, but another member of hedgehog family within Glires.

There are two extant hedgehog tenrecs (HHTs):
the greater HHT (Setifer = Ericulus setosus) and the lesser HHT (Echinops telfari). Their skulls are not that different from each other, except in size. They have similar skeletons and spines coats. So we’ll focus on the lesser HHT as other workers have done before.

The problem is
the large reptile tree (LRT) nests Echinops rather convincingly with hedgehogs, like Erinaceus, within Glires, not with tenrecs like Tenrec (Fig. 1). Shifting Echinops to the tenrecs adds 30 steps to the LRT. Shifting the entire tenrec clade (ncluding the odontocetes) to the hedgehogs adds only 12 steps.

We’ve seen something like this before
when the purported tenrec, Potamogale (Du Chaillu 1860, Nicoll 1985; extant), the giant otter shrew that was supposed to be a tenrec, instead nested rather convincingly with shrews, far from tenrecs. It, too, has a cloaca.

Maybe it’s because they’re all from Madagascar.
Not sure what it is about that island that takes a perfectly good set of genital and anal openings and reverts them back into a single primitive cloaca. But that appears to be happening here among unrelated taxa, by convergence.

Among mammals
monotremes have a cloaca and that is most likely the primitive condition, as a cloaca is found in all other reptiles. Most marsupials separate the anus and genitals, so no cloaca is present — except in the very derived marsupial moles. Marsupials are basal to placentals according to the LRT, so any appearance of a cloaca in placentals is a reversal. Thus the Madagascar hedgehogs, the African golden moles and giant otter shrews (Potamogale) that redevelop a cloaca are examples of phylogenetic reversals.

So you  have a choice in nesting these purported tenrecs:

  1. Do you follow the bones and other soft (and prickly, Fig. 2) tissue with the exception of the cloaca?
  2. Or do you follow the cloaca alone? Current taxonomy and experts for over a century favor this choice.

To my knowledge,
mtDNA studies have not been conducted yet to resolve interrelationships among tenrecs and other mammals. If Echinops is indeed a hedgehog, then tenrecs have not been genetically tested against odontocetes. In fact, tell me if I’m wrong, but this may be the first time such a study has been conducted on morphology alone. Asher and Hofreiter 2006 stated at the time: “Due in part to scarcity of material, no published study has yet cladistically addressed the systematics of living and fossil Tenrecidae (Mammalia, Afrotheria).”

Echinops was employed by Mouchaty et al. 2000. Echinops might have been used by Meredith 2011 and Song 2012 to nest tenrecs with golden moles (Chrysocloris) as Afrotheres, related to elephants (Elephas) and hyraxes (Procavia). I don’t see any other tenrecs being used in molecular studies.

Echinops was recently employed by
Suarez 2009 in a study of the vomernasal system (VNS). The distribution of both vomernasal pathways in Eutheria was found to be present in rodents and Echinops, but not in other tested eutherians, none of which included other tenrecs. Of course, hedgehogs nest with rodents in the LRT.

Figure 1. The skulls of Erinaceus (above), Echinops (middle) and Tenrec (below), compared. Note the large premaxillary teeth common to all members of the Glires to the exclusion of other clades, including Tenrecidae.

Figure 3. The skulls of Erinaceus (above), Echinops (middle) and Tenrec (below), compared. Note the large premaxillary teeth common to all members of the Glires to the exclusion of other clades, including Tenrecidae. The anterior maxillary tooth of Erinaceus might be a canine, but it is not at the anterior rim of the maxilla, where one expects a canine.

Let’s compare
a hedgehog, a tenrec and the lesser hedgehog tenrec and perhaps you’ll see that a mistake was made over 100 years ago that continues to adversely affect phylogenetic analyses today. Perhaps a member of Glires has been long considered a member of Tenrecidae by virtue of its location, Madagascar, and its cloaca.

The European hedgehog
Erinaceus europaeus (Linneaus 1758; 20-30cm; extant) this omnivore can roll itself into a ball, erecting its spines for defence. Unlike most Glires, the hedgehog does not have a diastema. The jugal is very tiny in this clade.

The lesser hedgehog tenrec
Echinops telfairi (Martin 1838; extant, 13-17 cm) the lesser or pygmy hedgehog tenrec is widely considered a tenrec, but here it nests with hedgehogs and other Glires including rodents. This omnivore is restricted to Madagascar, home of severalt tenrecs. Note the large canines, like tenrecs and unlike hedgehogs. Note the large premaxillary teeth, like hedgehogs and unlike tenrecs. Unlike tenrecs, the ears are prominent. Like tenrecs, the jugal is absent.

Given that the Madagascar mammals with a cloaca
all do some burrowing, I wonder if the genitals and anus retreated beneath the cover of a single opening in order to keep dirt out? If that’s not the answer, I wonder what the common thread is that these unrelated taxa have that caused that primitive trait to reappear? And I wonder if there are any analyses based on morphology that include several tenrecs and other eutherians for comparison? So far I have found none, so the LRT is shedding light where it may be needed.

If Echinops is indeed a hedgehog with a cloaca
then we have to go get some mtDNA from Tenrec to see if it is a good match for odontocete mtDNA. At present, Tenrec has not been tested for its mtDNA, that I know of, so the whale connection question remains open.

While we’re at it it
count the stomachs in Tenrec. Even odontocetes have subdivided stomachs. Let’s find out when that trait appeared.

Asher RJ 2007. A web-database of mammalian morphology and a reanalysis of placental phylogeny. BMC Evol Biol. 7: 108-10 online
Asher  RJ and Helgen KM 2010. Nomenclature and placental mammal phylogeny. BMC Evolutionary Biology 10:102 online
Du Chaillu P 1860. Descriptions of mammals from equatorial Africa. Proceedings of the Boston Society of Natural History, 7, 358–369.
Eisenberg JF and Gould E 1970. The tenrecs: a study in mammalian behavior and evolution. Smithsonian Institution Press, Washington, DC. 138 pp. PDF online
Linnaeus C 1758. Systema naturæ per regna tria naturæ, secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis. Tomus I. Editio decima, reformata.
Martin WCL 1838. On a new genus of insectivorous mammalia. Proceedings of the Zoological Socieety, London, 6:17.
Mouchaty SK, Gullberg A, Janke A, Arnason U 2000. Phylogenetic position of the Tenrecs (Mammalia: Tenrecidae) of Madagascar based on analysis of the complete mitochondrial genome sequence of Echinops telfairi. Zoologica Scripta. 2000, 29 (4): 307-317. 10.1046/j.1463-6409.2000.00045.x.
Nicoll M 1985. The biology of the giant otter shrew *Potamogale velox*. National Geographic Society Research Reports, 21: 331-337.
O’Leary, MA et al. 2013. The placental mammal ancestor and the post-K-Pg radiation of  placentals. Science 339:662-667. abstract
Suárez R, Villalón A, Künzle H and Mpodozis J 2009. Transposition and Intermingling of Gαi2 and Gαo Afferences into Single Vomeronasal Glomeruli in the Madagascan Lesser Tenrec Echinops telfairi. PLoS ONE 4(11): e8005. doi:10.1371/journal.pone.0008005


11 thoughts on “The ‘hedgehog’ tenrecs: they nest with hedgehogs

  1. And here’s a prime example of science working by finding congruence of independent variables. Molecular analyses have indeed been performed for tenrecs, such as Poux et al. (2008), which found Echinops groups with Tenrec extremely strongly (six combined nodes each supported by >90% maximum liklihood and >99% posterior probability keep it from non-afrotherians). Note an odontocete, Potamogale and a Eulipotyphla that is mostly Erinaceus are included. Then you look at biogeography, which matches Afrotheria and Tenrecidae. And the cloaca also matches, which as you note really doesn’t make sense as a systematic reversal of every Malagasy ‘insectivore’. The burrowing excuse doesn’t work since moles or the tons of burrowing rodents don’t revert to a cloaca AFAIK.

    As for “MASSIVE convergence involving everything but the cloaca” being our alternative, and ” tell me if I’m wrong, but this may be the first time such a study has been conducted on morphology alone”, you do realize that the Asher and Hofreiter (2006) study you quote right afterwards includes a morphology-only analysis of 126 characters (figure 6)? Echinops groups with Tenrec instead of Erinaceus with a 99% posterior probability. I’d be willing to bet that your analysis designed for a basic amniote tree doesn’t include almost any of the characters used in Asher’s matrix that’s designed to recover placental mammal and ‘insectivore’ relationships, and that your morphological interpretations are off. As an independent source, note Halliday et al.’s (2015) morphology-only analysis of 680 characters found Potamogale to be far from Pakicetus and Rodhocetus.

    So really the question is- Are molecules, biostratigraphy and anatomy as coded by experts (using multiple specimens examined by hand- Appendix 1 of Asher and Hofreiter- 22 Echinops, 13 Erinaceus, etc.) in studies designed to answer this question right, OR are your results as a novice to mammalian anatomy (using images found online) coded in your general amniote matrix good enough to counter that?

    References- Asher and Hofreiter, 2006.

    Poux et al., 2008.

    • ^ all this. Research has been done, and this article is WAY too simple and focussing on certain points while forgetting or ignoring the complete picture. Convergent evolution is a thing. But on top of that there is so much more that should be taken into account – the animal is more than just bones, skin and DNA.
      Yes they have quills (the lesser and greater hedgehog tenrec) which make them look similar to hedgehogs. Yes some parts of their skull might look similar. But that doesn’t mean they are related. There’s also differences in behaviour, mating, raising young, etc. to account for, on top of the genetics.

      As someone with first-hand experience with several hedgehog and tenrec species I can say that (on top of the other evidence), these animals might look similar but are very different.

      By the way – lesser hedgehog tenrecs are (semi)arboreal and excellent climbers. They do not burrow like e.g. T. ecaudatus. A hedgehog burrows more than Echinops does, and they don’t have a cloaca.

      “If that’s not the answer, I wonder what the common thread is that these unrelated taxa have that caused that primitive trait to reappear?”

      Tenrecs are extremely primitive mammals. Who says that trait reappeared instead of the other way around – a newer trait (two openings) never appeared at all?
      Also, hedgehogs are not a member of Glires. Focussing on just the skeleton and outside appearance is way too simplistic and this article shows how it can set things off the wrong foot.

      • Sorry for the late reply. I’m just getting to my emails.
        I don’t have answers for your queries, but I do know that in phylogenetic analysis, given the present taxon and character lists, this is how tenrecs split up. The present list was capable of separating hard shell from soft shell turtles, all the Solnhofen birds once labeled Archaeopteryx, baleen from toothed whales and seals fro sea lions. If you have access to a genus-based morphological analysis that keeps putative tenrecs together and also includes most of the present taxon list of potential candidates, please send it to: I eagerly look forward to it. Until then, I have to stand by my results, but eager to change them when valid data upsets the present topology.

  2. I wonder, are you purposefully ignoring pretty much everything I’ve said as well as the first reply from Mickey Mortimer? You are only looking at a skull. There are similarities between those of Echinops and hedgehogs, and there are similarities between those of Echinops and other tenrecs. So that’s what you are basing your hypothesis on? Just a skull? No regards for everything else, including molecular analyses?
    I understand it’s easy to jump to conclusions when seeing both skulls, but let’s not forget the complete picture here.

    Even abilities in terms of movement between Echinops and hedgehogs are vastly different (e.g. grooming). Anyone who has seen these animals in the flesh up close (which you haven’t, as far as I am aware – correct me if I’m wrong) and is familiar with both species will notice the differences. If you add everything up you won’t get your outcome.
    T. ecaudatus has quills as well, but that doesn’t make it related to hedgehogs (or porcupines for that matter) either. It is never about just one trait, like I said it’s the complete picture.

    I haven’t read up on your tenrec/odontocete connection but I might, so I can’t say much about it now.

  3. Another reason why this sort of comparison doesn’t hold up well – “This omnivore is restricted to Madagascar, home of severalt tenrecs. Note the large canines, like tenrecs and unlike hedgehogs. Note the large premaxillary teeth, like hedgehogs and unlike tenrecs. Unlike tenrecs, the ears are prominent. Like tenrecs, the jugal is absent.”

    I could do this comparison with many animals… There are tenrec species with prominent ears and ones that are less prominent. There are hedgehog species with prominent ears (e.g. Hemiechinus auritus) and less prominent ears (Erinaceus europaeus – the one you are using for comparison here).
    It seems like the differences between species of a certain genus or family aren’t taken into account; you can’t just pick and choose one that fits your narrative.

    • You’re absolutely right. I was cherry-picking traits in order to make the differences simple for my readers. In this context, I hope you can understand my reasons for doing so. The real deal, as always, is found in the 231 traits of the LRT that the software recovered.

  4. Thank you for your comment. The LRT is an experiment in scoring morphological characters as they are, based on data available to me. Thereafter I present the results. That’s what I’m supposed to do. Taxa that nest together here for the first time all too frequently are tested together here for the first time. DNA produces false positives as shown in primate studies and elsewhere as you’ve noted.

    Please send post-crania if you have it and I will enter it. I don’t include soft tissue presently and have no plans to do so in the future. I agree, the spines of the tenrec are not homologous with those of the hedgehog.

    You wrote: “you can’t just pick and choose one that fits your narrative” Actually I have used the same characters since testing the first 200 taxa. So there is no cherry picking of traits here. The software recovers the results. If I find mistakes, I fix them. Let me know which taxa should nest together and you are welcome to pick and choose traits that fit your narrative. I realize that’s a lot of work. It might be simpler to take the images offered at, put two or four together and make notes in Photoshop and send them over.

    • No post-crania – all my current tenrecs are alive and well, fortunately.
      I stumbled upon this article while browsing the internet and I’d never heard about your LRT before but I have been looking into it a bit – I’m afraid I must say I don’t agree with most of it and discovered the whole thing and some of your previous work is quite controversial, to say the least; I’m not the only one it seems. The LRT and this article say enough for me – it doesn’t make much sense. I wish you the best with your work though even if I think it’s heading in the wrong direction.

  5. Doesn’t make much sense… in what sense? Take a another look. All the sister taxa look alike in their skeletons. That can’t be said of competing studies where the two too often differ greatly. I’ll make changes if you can validate your suggestions with data.

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s