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Grampus griseus joins the globicephalines

The views expressed are those of the author and are not necessarily those of Scientific American.


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Photo by Douglas Eernisse, University of California (Santa Cruz).

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Thanks to everyone who had a go at identifying the Baja California whale carcass. Some suggestions were, err, a little far of the mark (fin whale, mesoplodont beaked whale); others were pretty reasonable (pilot whale). So, what do we have? Answer: a toothed cetacean (that is, an odontocete), total length about 3 m, with a large, subtriangular dorsal fin, a blunt head, and a strongly reduced dentition. The photos clearly showed that dentition is absent in the upper jaws, and that the lower jaws have just two or three short, subconical teeth on each side. The carcass is greyish, but it’s difficult to know if this really reflected the colour in life.

One cetacean – and one cetacean alone – matches these listed characters: Risso’s dolphin Grampus griseus (sometimes known as the Grey dolphin or Grey grampus). Well done Cameron McCormick, suferable, vdinets, leecris, Hai-Ren, Dartian, Mark Evans and Phoca, all of whom correctly said Risso’s dolphin. Regarding other possible matches… pilot whales (Globicephala), False killer whales Pseudorca crassidens, Pygmy killer whales Feresa attenuata and Melon-headed whales Peponocephala electra all have both a higher numbers of teeth overall and emergent teeth in the upper jaw, and all are much darker in living condition.

Life-size Risso's dolphin model, on display at the Natural History Museum, London.

So, the carcass is definitely that of a Risso’s dolphin. A few features normally present in life are not obvious on the carcass. These include a distinctive white, anchor-shaped marking on its chest, and a vertical crease on the forehead. The latter feature is highly distinctive and not seen in other blunt-headed delphinids. Phillips et al. (2003) suggested that it allows the dolphin to create a uniquely angled sonar beam. Unusual specimens with emergent teeth in the upper jaws have been reported on occasion (Kruse et al. 1999) but the typical condition is to have two to seven pairs of teeth in the lower jaws and apparently one or two pairs of unerupted upper jaw teeth.

This is a widespread dolphin, found in tropical, subtropical and temperate oceans and seas worldwide. In contrast to several other globally widespread dolphin ‘species’, molecular variation between populations is low, being about 0.2% (LeDuc et al. 1999). This is consistent with the fact that – in contrast to other globally distributed delphinid ‘species’ – there have not yet been recent proposals to split G. griseus into more than one species.

Risso's dolphin photographed off California by Mike Baird.

Risso’s dolphin seems to show a preference for oceanic canyons and continental slope environments and there are indications that it takes advantage of upwelling phenomena and the movement of oceanic fronts up and down continental slopes (Baumgartner 1997, Bearzi et al. 2011) [adjacent photo by Mike Baird]. It often feeds at night. While its ecology and natural history haven’t really been well studied, reliable data show that it’s a cephalopod specialist (Clarke 1986), mostly eating mesopelagic squid and also octopuses. Stomach content data indicates that fish and tunicates are eaten as well, sometimes, in some places. In prey requirements, morphology and habitat choice, Risso’s dolphin is very similar to the Short-finned pilot whale Globicephala macrorhynchus and there are indications that the two avoid competing by segregating (Shane 1995). When they do meet, interactions are aggressive.

More life-size cetacean models at London's NHM, with the Risso's dolphin down at the bottom. Note the pale markings on the underside of the pilot whale at top left - we'll be coming back to this later. Click to enlarge.

Risso’s dolphin is one of the largest delphinids, with some individuals reaching 4 m and 500 kg. Males and females are similar in size and adults of both sexes are always conspicuously marked with numerous white scars across their bodies and tails. Some of these might result from grappling with cephalopods, but the majority are tooth marks made by other individuals. The ubiquity and number of these score marks show that biting or – at least – ‘scoring’ with the mandibular dentition is a commonplace activity in these dolphins, perhaps occurring as part of play and courtship as well as combat. Some individuals are so scarred that they’re white across much of their dorsal surface.

Risso’s dolphin was first recognised scientifically in 1812 when George Cuvier described a skin and skull discovered at Brest in France. He recognised that it represented a new species and named it Delphinus griseus. At about the same time, Cuvier also obtained a description (with drawing) of another distinctive dolphin that stranded near Nice. This report came from a M. Risso, so Cuvier took to referring to the animal as ‘dauphin de Risso’. He named it D. aries, apparently “because the drawing showed that this dolphin had a creased forehead something like the horn boss on a ram’s head” (Watson 1988, p. 254). It’s been near-universally agreed for some decades now that both specimens belonged to the same species, so the vernacular name ‘Risso’s dolphin’ became transferred to D. griseus.

Skull and mandible of Grampus griseus, specimen BMNH SW1938, photo courtesy Colin McHenry (c) NHM. Note that this specimen has an emergent tooth in the upper jaw. Click to enlarge.

In 1828, John Gray decided that D. griseus and a number of other blunt-headed delphinids should be given their own ‘subgenus’, Grampus. This name – once widely used as the vernacular term for various blunt-headed delphinids – seems to derive from a corruption of the French ‘grand poisson’. Gray’s version of Grampus at times included pilot whales, false killer whales and killer whales as well as species later moved to Lagenorhynchus and Cephalorhynchus, and in addition to G. griseus he and others also named the species G. sakamata Gray, 1846, G. richardsoni Gray, 1850 (based on a lower jaw of unknown origin), G. chinensis Gray, 1866 and G. stearnsii Dall, 1873 (also based on a lower jaw). All of these names (and others) are now included in the synonymy of G. griseus (Hershkovitz 1966).

There have been a couple of misguided attempts to come up with new generic names for Grampus. Grayius Scott, 1873 was proposed since Grampus was deemed inappropriate; Iredale and Troughton (1933), similarly, decided that the name Grampus should be applied specifically to Orcinus orca, the Killer whale, and they therefore proposed the new generic name Grampidelphis for Risso’s dolphin. Their arguments were erroneous; Hershkovitz (1961) said “All this and more too painful to recite is sheer fantasy” (p. 549).

Long-finned pilot whale (Globicephala melas) showing characteric features associated with globicephalines (blackness, bulbous melon, absent rostrum). Image from wikipedia.

Risso’s dolphin is very obviously a true dolphin – that is, part of the delphinoid clade Delphinidae. But where might it belong within this large and morphologically diverse group? Despite its blunt head and lack of a long beak or rostrum*, it has – ignoring confusion from before the 20th century – traditionally not been included within the ‘globicephaline’ group often recognised for pilot whales and other ‘blackfish’. Some authors have included killer whales (Orcinus) within Globicephalinae, and have therefore used the name Orcininae for this group (the latter is Orcininae Wagner, 1846; the former Globicephalinae Gray, 1850). Obviously, globicephalines are mostly black [adjacent pilot whale illustration from here]. Risso’s dolphin isn’t, and I think this partly explains why it hasn’t typically been regarded as a member of the group. But it’s said to exhibit several features of palatal sinus anatomy that are shared with Delphinus and kin (Muizon 1988). Until recently, Risso’s dolphin has, therefore, been included within Delphininae, typically being hypothesised to be closer to Delphinus and Stenella than to the ‘lags’ (= lissodelphinines) or to the ‘stenines’.

* The rostrum is not truly absent in Risso’s dolphin, it’s just very short and not clearly demarcated from the rest of the head.

Delphinoid section of Geisler et al.'s (2011) cladogram. Note the position of Grampus.

However, recent molecular studies do not support a delphinine position for Grampus. In the earliest comprehensive analyses of molecular phylogeny within delphinids, LeDuc et al. (1999) proposed several novel, surprising hypotheses, one being that Grampus is not close to the long-beaked dolphins (Delphinus, Stenella and kin*), but is instead a globicephaline, most closely allied with Pseudorca (false killer whale), Feresa (pygmy killer whale), Peponocephala (melon-headed whale) and Globicephala (pilot whales). [Caveat: I’m using the name Globicephalinae here as if it’s branch-based, and thus that any delphinid closer to Globicephala than to Delphinus or Lagenorhynchus is a globicephaline. Some authors seem to use the name as if it’s unique to the ‘blackfish’ clade. Given that there are no explicit phylogenetic definitions anywhere in the literature (so far as I can tell), it’s difficult to know exactly what to do.]

* All of which (Delphinus, Tursiops, Stenella and Lagenodelphis) are potentially ripe for synonymisation according to these authors (LeDuc et al. 1999).

Rough-toothed dolphin (Steno bredanensis), photo by NOAA, from wikipedia. Sure doesn't look like the other globicephalines... Richard Ellis said that it looks like an ichthyosaur.

McGowen et al. (2009) recovered evidence for a similar clade, though Orcaella (snubfin dolphins) was now recovered as the sister-taxon to the others and, surprisingly, Steno (the peculiar rough-toothed dolphin) was positioned in between Orcaella and the remainder recovered as being closer to Grampus and the ‘blackfish’ than was Orcaella (McGowen et al. 2009). Both the long-beaked delphinines and the lissodelphinines were closer to this clade than was Orcinus, the killer whales. Extremely similar results have been reported in other studies (Caballero et al. 2008, Cunha et al. 2011, McGowen 2011, Geisler et al. 2011). In fact we can now say that the position of Grampus within Globicephalinae is well supported and represents the present consensus. Incidentally, Steno was taken away from the globicephalines and put close to the long-beaked delphinines by Cunha et al. (2011).

Time-calibrated cetacean phylogeny, from Cunha et al. (2011). Hopefully you can see the divergence dates for Grampus and other members of the globicephaline lineage.

McGowen et al. (2009) estimated that Grampus diverged from other globicephalines round about 5 million yeas ago (early on in the Pliocene) while Cunha et al. (2011) similarly suggested (based on relaxed molecular clock calibration) a divergence date of 5.5 million years ago. Fossil specimens of Grampus are rare but there’s supposed to be one from the Early Pliocene of Japan and a Pleistocene record from Madagascar.

Some speculations about sinus form, snout shape and pigmentation

The pterygoid sinus patterns of (a) Globicephala, (b) Steno, (c) Lagenorhynchus (sensu lato), (d) Grampus, (e) Tursiops, (f) Stenella, and (g) Delphinus. From Muizon (1988), itself based on the figure in Fraser & Purves (1960). Click to enlarge.

What does this mean for delphinid evolution? It suggests several interesting things. One is that pterygoid sinus morphology – the sole anatomical character complex used to ally Grampus with long-beaked delphinines – is seemingly less reliable than classically thought. That might not be surprising given evidence from elsewhere in the tree of life that the development of sinuses and air-sacs is labile and opportunistic. I think in any case that the complex sinus system of Grampus is only superficially similar to that of long-beaked delphinines: when I look at the sinus configurations illustrated by Fraser & Purves (1960), the Grampus condition looks like an elaborate version of the simpler condition present in pilot whales, and not especially like that of Tursiops, Stenella and Delphinus.

Another interesting thing concerns snout shape (and note here that, by ‘snout shape’, I refer to the condition in the living animal: that is, where the melon and its associated soft tissues envelop much of the length of the bony rostrum). Consider that porpoises and monodontids (narwhals and belugas) are close relatives of delphinids and, as we’ve just seen, most recent phylogenetic studies find killer whales and lissodelphinines (Cephalorhynchus and the ‘lags’ and so on) to be outside the globicephaline + long-beaked delphinine clade.

Delphinid rostra as seen in dorsal view: (a) Globicephala, (b) Pseudorca, (c) Peponocephala, (d) Orcaella, (e) Orcinus. From Muizon (1988). Globicephala (pilot whales) is strangest in having such anteriorly broad premaxillae. And remember that molecular phylogenies do not recover Orcinus (killer whales) as a close relative of the others shown here. Click to enlarge.

Notably, all of these groups are short-snouted, or at best ‘medium-snouted’ (though, long-beaked fossil porpoises do confuse the picture somewhat). Could it be, therefore, that short snouts were ancestral for delphinids and widespread during most of their history, that globicephalines were primitively short-snouted (that is, they did not evolve from long-snouted ancestors), and that long snouts were only evolved at the base of the delphinine lineage? On balance, I think it’s safest to assume that modest, mid-length snouts were the norm for most of delphinid history. Globicephalines might not be as unusual (in being blunt-headed) as people used to think, but they’re still modified relative to the ancestral condition in having an especially wide bony rostrum (this is most evident in pilot whales and false killer whales) and an enlarged, anteriorly prominent melon.

Finally, what about pigmentation? Morphological character sets on extant species often neglect to include or code pigmentation data, but – while undeniably labile – it clearly carries a phylogenetic signal (and tests involving coat patterns in cats and other groups often produce encouraging results). As is obvious from the vernacular term ‘blackfish’, globicephalines are unusual among delphinids in being mostly black. If Grampus and Orcaella are part of Globicephalinae [see caveat above], but outside the ‘blackfish’ clade (Pseudorca, Feresa, Peponocephala and Globicephala), then we might infer that the greyish Grampus and Orcaella represent the primitive condition. In fact (time for some rampant speculation), Grampus is born dark and becomes paler with age, only retaining the darker pigmentation on its fins, flukes and dorsal fin (and sometimes on the chin as well). Could the dark overall colouration in the blackfish perhaps be a paedomorphic feature?

Spyhopping pilot whale, showing pale chest patch similar to that present in Risso's dolphin. Photo by Barney Moss, from wikipedia.

Also interesting is that Grampus has a wide, white area on its chest, joined by a thin ‘stem’ to another wide, white area on its belly. The same, ‘anchor-shaped’ configuration is present in pilot whales, false killer whales, pygmy killer whales and melon-headed whales: in these taxa the ‘stem’ is longer, the abdominal field is smaller, and the ‘anchor’ is sometimes greyish or off-white rather than pure white [adjacent pilot whale image by Barney Moss]. Nevertheless it’s conceivable that this is a shared derived character.

As usual, what was meant to be a quick, couple-hundred-words-article saying “Yes, it was a Risso’s dolphin” evolved in something with a bit more substance. I hope you learnt something!

For links to ALL previous Tet Zoo cetacean articles (there are quite a few of them), please see…

Refs – -

Baumgartner, M. F. 1997. The distribution of Risso’s dolphin (Grampus griseus) with respect to physiography in the northern Gulf of Mexico. Marine Mammal Science 13, 614-638.

Bearzi, G., Reeves, R. R., Remonato, E., Pierantonio, N. & Airoldi, S. 2011. Risso’s dolphin Grampus griseus in the Mediterranean Sea. Mammal Biology 76, 385-400.

Caballero, S., Jackson, J., Mignucci-Giannoni, A. A., Barrios-Garrido, H., Beltrán-Pedreros, S., Montiel-Villalobos, M. G., Robertson, K. M., Baker, C. S. 2008. Molecular systematics of South American dolphins Sotalia: sister taxa determination and phylogenetic relationships, with insights into a multilocus phylogeny of the Delphinidae. Molecular Phylogenetics and Evolution 46, 252-268.

Clarke, M. R. 1986. Cephalopods in the diet of odontocetes. In: Bryden, M. M. & Harrison, R. (eds.) Research on Dolphins. Claredon, Oxford, pp. 281-321.

Cunha HA, Moraes LC, Medeiros BV, Lailson-Brito J Jr, da Silva VM, Solé-Cava AM, & Schrago CG (2011). Phylogenetic status and timescale for the diversification of Steno and Sotalia dolphins. PloS one, 6 (12) PMID: 22163290

Fraser, F. C. & Purves, P. E. 1960. Hearing in cetaceans: evolution of the accessory air sacs and the structure and function of the outer and middle ear in recent cetaceans. Bulletin of the British Museum (Natural History) 7, 1-140.

Geisler, J. H., McGowen, M. R., Yang, G. & Gatesy, J. 2011. A supermatrix analysis of genomic, morphological, and paleontological data from crown Cetacea. BMC Evolutionary Biology 2011, 11:112 http://www.biomedcentral.com/1471-2148/11/112

Hershkovitz, P. 1961. On the nomenclature of certain whales. Fieldiana : Zoology 39, 547-565.

- . 1966. Catalog of living whales. Smithsonian Institution United States National Museum, Bulletin 246, 1-259.

Iredale, T., & Troughton, E. Le G. 1933. The correct generic names for the Grampus or Killer Whale, and the so called Grampus or Risso’s Dolphin. Records of the Australian Museum 19, 28-36.

Kruse, S., Caldwell, D. K. & Caldwell, M. C. 1999. Risso’s dolphin Grampus griseus (G. Cuvier, 1812). In Ridgway, S. H. & Harrison, R. (eds.) Handbook of Marine Mammals, vol. 6, The Second Book of Dolphins and Porpoises. Academic Press, San Diego, pp.183-212.

LeDuc, R. G., Perrin, W. F. & Dizon, A. E. 1999. Phylogenetic relationships among delphinid cetaceans based on full cytochrome b sequences. Marine Mammal Science 15, 619-648.

McGowen, M. R. 2011. Toward the resolution of an explosive radiation – a multilocus phylogeny of oceanic dolphins (Delphinidae). Molecular Phylogenetics and Evolution 60, 345-357.

- ., Spaulding, M., Gatesy, J. 2009. Divergence date estimation and a comprehensive molecular tree of extant cetaceans. Molecular Phylogenetics and Evolution 53, 891-906.

Muizon, C. de 1988. Les relations phylogénétiques des Delphinida (Cetacea, Mammalia). Annales de Paléontologie (Vert.-Invert.) 74, 159-227.

Philips, J. D., Nachtigall, P. E., Au, W. W., Pawloski, J. L. & Roitblat, H. L. 2003. Echolocation in the Risso’s dolphin, Grampus griseus. Journal of the Acoustical Society of America 113, 605-616.

Shane, S. H. 1995. Relatioship between pilot whales and Risso’s dolphins at Santa Catalina Island, California, USA. Marine Ecology Progress Series 123, 5-11.

Watson, L. 1988. Whales of the World. Hutchinson, London.

Darren Naish About the Author: Darren Naish is a science writer, technical editor and palaeozoologist (affiliated with the University of Southampton, UK). He mostly works on Cretaceous dinosaurs and pterosaurs but has an avid interest in all things tetrapod. His publications can be downloaded at darrennaish.wordpress.com. He has been blogging at Tetrapod Zoology since 2006. Check out the Tet Zoo podcast at tetzoo.com!

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The views expressed are those of the author and are not necessarily those of Scientific American.





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  1. 1. Cameron McCormick 11:52 am 02/27/2012

    globicephalines are unusual among delphinids in being mostly black

    However some photographs of Feresa show them as light brown with a dark brown cape. Maybe there’s some regional variation, but I suspect most photographs and observations were not under ideal lighting conditions similar to how Cephalorhynchus eutropia was erroneously thought to be black. Peponocephala also seems to be far more gray than black,

    Link to this
  2. 2. naishd 12:05 pm 02/27/2012

    Wow, I really thought that Feresa was always black, thanks. I mean, the presence of a ‘dorsal cape’ is well known, but even Watson (1988) – who had enhanced colour perception when it came to live cetaceans – said “The colour is black” (p. 219). “Deep grey” has been described for Peponocephala (Watson 1988, p. 221). And, no, I don’t usually rely on Watson (1988), but I have it to hand.

    I note that some ziphiids look a different colour depending on where they’re photographed. There are photos of Berardius arnuxii (taken in tropical waters) where it looks brown, and others (taken in polar waters) where it looks blackish blue. On a similar note, I’ve heard people say that the different colours reported for the two coelacanth species might be due to local lighting conditions (no idea how realistic that is, but people have said it).

    Darren

    Link to this
  3. 3. Cameron McCormick 12:56 pm 02/27/2012

    Watching this video of (evidently polar) B. arnuxii they look very dark from a distance but up close seem grayish and/or brownish.

    I’ve seen photographs of both coelacanth species exhibiting brown and blue coloration (and some exhibiting both) and I suspect it’s due to some combination of variation, postmortem color change, being in or out of the water, and lighting.

    Link to this
  4. 4. Boesse 3:40 pm 02/27/2012

    Can’t believe I missed the first post! Anyway – a few comments [sorry this got so long!]. First, there has never really been much support in cladistic analyses of the delphinids for inclusion of Orcinus within the Globicephalinae, and it’s mostly a historical inclusion based on large size, black color, and a number of other morphological features. Molecular results have been less encouraging than morphological studies, and the analysis by Geisler et al. shows it as one of the earliest diverging delphinids.

    With regards to rostral shape amongst delphinoids – it depends upon what you call a delphinoid and what the basal most members are. All of our fossil monodontids are Messinian or younger, and critters like the late Miocene Denebola are already fairly derived; I would not be surprised, for example, if we found middle Miocene monodontids with elongate rostra. “Kentridontid” dolphins like Atocetus, Albireo, Kentriodon, Liolithax, and a whole host of other Miocene taxa all have elongate rostra, and are either basal delphinoids or are just outside delphinoidea (depending upon which node you use), based on some phylogenetic analyses (although Kentridon itself appears as a basal branch within the Delphinida in Geisler et al.). There is an undescribed basal delphinid from the Tortonian of southern California with an elongate rostrum, but it unfortunately is undescribed. And of course as you alluded to, most fossil porpoises have elongate, delphinid-like rostra (exceptions being Septemtriocetus and a couple of undescribed fossils from the California Pliocene… stay tuned).

    With regards to fossil globicephalines – in some phylogenetic analyses of globicephalines (e.g. Aguirre-Fernandez et al., 2009), Peponocephala (which has the narrowest rostrum on an extant globicephaline – but still “beakless”) and the extinct long-snouted (and superficially Tursiops-like) globicephaline Hemisyntrachelus – are the basal most globicephalines. Otherwise, globicephalines have a rather “shallow” fossil history, going back about 4-6 Ma at the oldest (stay tuned for more on the early evolution of globicephalines…)

    Otherwise, your idea is pretty interesting and in your defense, certainly nearly as parsimonious as the alternative. There has been some debate regarding how many times suction feeding and “amblygnathy” has evolved within cetacea: Werth (2006), using rostral/mandibular bluntness as a correlate of suction feeding, suggested that suction feeding evolved in parallel numerous times within the odontoceti, but in a more detailed study which I certainly need to read more closely, Johnston and Berta (2010) indicated that suction feeding likely evolved once, primitively within the Neoceti or even within the Pelagiceti, and that “beak loss” (so to speak) evolved numerous times.

    G. Aguirre-Fernandez, L. G. Barnes, F. J. Aranda-Manteca and J. R. Fernandez-Rivera. 2009. Protoglobicephala mexicana, a new genus and species of Pliocene fossil dolphin (Cetacea; Odontoceti; Delphinidae) from the Gulf of California, Mexico. Boletin de la Sociedad Geologica Mexicana 61(2):245-265

    Johnston, C. and A. Berta (2010). Comparative anatomy and evolutionary history of suction feeding in cetaceans. Marine Mammal Science, doi 10.1111/j.1748-7692.2010.00420.

    Werth, A. J. 2006a. Mandibular and dental variation and the evolution of suction feeding in
    Odontoceti. Journal of Mammalogy 87:579–588.

    Link to this
  5. 5. Heteromeles 5:38 pm 02/27/2012

    Ummmm, wasn’t there a documented hybrid of Grampus X Tursiops truncatus? Was it sterile or fertile?

    Link to this
  6. 6. naishd 6:03 pm 02/27/2012

    Boesse/Bobby – thanks much for the lengthy comment (# 4). My comments are tangential to what you’ve said, not a response to them, but, anyway… the phylogeny generated by Aguirre-Fernández et al. (2009) – the Protoglobicephala description – is, hmm, interesting (and Post & Kompanke (2010), in their description of Platalearostrum, interpret their new taxon within that phylogeny). What I mean is that it’s really unusual in view of the fact that (as you note) the several molecular phylogenies discussed above find Orcinus to be well removed from Globicephalinae, whereas it’s nested within this clade according to Aguirre-Fernández et al. (2009). This seems to me to be the result of a tiny data set: 10 taxa and just 21 characters! On the first point, there are no lissodelphinines and only Kentriodon as a non-delphinid, so any included taxon that isn’t a long-beaked delphinine basically has to be recovered as a globicephaline. This could explain why the most ‘delphinine-like’ of the included globicephalines were recovered as ‘most basal’. In other words, not compelling. At least some of their characters come from Bianucci’s papers – I have a really hard time getting hold of these. Does anyone know if Palaeontographica Italica is available online?

    A trivial thing: given uncertainty and ambiguity over the use of names like Globicephalinae and Orcininae, will someone please make sure they publish some explicit phylogenetic definitions! Lots of tetrapod clades are afflicted with this problem.

    Darren

    Refs – -

    Aguirre-Fernández, G., Barnes, L. G., Aranda-Manteca, F. J. & Fernández-Rivera, J. R. 2009. Protoglobicephala mexicana, a new genus and species of Pliocene fossil dolphin (Cetacea; Odontoceti; Delphinidae) from the Gulf of California, Mexico. Boletín de la Sociedad Geológica Mexicana 61, 245-265.

    Post, K. & Kompanje, E. J. O. 2010. A new dolphin (Cetacea, Delphinidae) from the Plio-Pleistocene of the North Sea. Deinsea 14, 1-13.

    Link to this
  7. 7. naishd 6:31 pm 02/27/2012

    Heteromeles (comment 5): alleged wild Grampus x Tursiops hybrids, stranded on the coast of Ireland in 1933, were reported by Fraser (1940). On morphological grounds, they seemed like ‘good’ hybrids, but their identification was (for obvious reasons) never confirmed genetically, so these days there are some who express scepticism. A few other hybrids are known from captivity (Shimura et al. 1986, Miyazaki et al. 1992). The most recent I’m aware of was born in China in June 2011 but died during birth.

    Darren

    Refs – -

    Fraser, F.C. 1940. Three anomalous dolphins from Blacksod Bay, Ireland. Proceedings of the Royal Irish Academy, Section B 45, 413–-455.

    Miyazaki, N., Hirosaki, Y., Kinuta, T. & Omura, H. 1992. Osteological study of a hybrid between Tursiops truncatus and Grampus griseus. Bulletin of the National Science Museum Series A (Zoology) 18, 79–-94.

    Shimura, E., Numachi, K., Sezaki, K., Hirosaki, Y., Watabe, S., & Hashimoto, K. 1986. Biochemical evidence of hybrid formation between the two species of dolphin Tursiops truncatus and Grampus griseus. Bulletin of the Japanese Society of Scientific Fisheries 52, 725–-730.

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  8. 8. Dartian 2:01 am 02/28/2012

    Darren:
    what was meant to be a quick, couple-hundred-words-article saying “Yes, it was a Risso’s dolphin” evolved in something with a bit more substance

    I’m particularly impressed by the fact that you are able to write a popular article of this length about Risso’s dolphin without even once mentioning Pelorus Jack. ;)

    “Steno (the peculiar rough-toothed dolphin) was phylogenetically intermediate between Orcaella and the remainder

    Er, no. In McGowen et al‘s. paper, Steno isn’t “phylogenetically intermediate” between those taxa; it’s the sister taxon of (i.e., more closely related to) the “remainder”.

    More generally speaking, I’m not certain if it’s even theoretically possible for a species/clade to be truly phylogenetically ‘intermediate’ between two others (let’s ignore interspecific hybridization events which take place at the level of individuals). Would hard polytomies (assuming that such things ‘really’ exist) qualify? What sayeth David Marjanović?

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  9. 9. naishd 4:03 am 02/28/2012

    Oh, come on.. I just used a bad choice of wording (and will now go change it). I meant that it’s positioned with Orcaella on one side, and the other globicephalines on the other.

    Darren

    Link to this
  10. 10. naishd 4:05 am 02/28/2012

    As for Pelorus Jack – you know that I try and avoid the stuff we’ve all heard about a million times before :) Seriously, it can be hard to find a popular book or article that mentions Risso’s dolphin and doesn’t mention Pelorus Jack.

    Darren

    Link to this
  11. 11. Jerzy New 5:36 am 02/28/2012

    You could write on less known aspect of cetacean behaviour – that they chase and kill smaller cetaceans to get rid of potential competitors for food. They also regularly fight and kill their own species.

    This parallels land carnivores like lions and wolves, of course. But somehow doesn’t fit with public image of dolphins and whales.

    Link to this
  12. 12. Dartian 5:41 am 02/28/2012

    Darren:
    I meant that it’s positioned with Orcaella on one side, and the other globicephalines on the other.

    But it isn’t really positioned “between” them! In a bifurcating cladogram, you could change places of the branch that leads to Steno and the branch that leads to ((((Globicephala+Peponocephala)+Feresa)+Pseudorca)+Grampus) and still have the exact same tree. And Orcaella, in turn, is exactly equally closely related to either branch.

    Link to this
  13. 13. naishd 5:44 am 02/28/2012

    Jerzy (comment 11): bottlenose dolphins kill porpoises and bully spotted dolphins (I think both cases are now very well known – they’ve been featured on TV quite a lot, for example)… but, yes, there are new cases, like the Risso’s dolphin killed by bottlenose dolphins last year. Is it definitely due to competition? The killing of porpoises by bottlenose dolphins was suggested to be due to mistaken identity by infanticidal males, while other people have said that some of the killings can’t be securely linked to competition over resources (note that bottlenose and Risso’s dolphin do not feed on the same prey in any case).

    Darren

    Link to this
  14. 14. naishd 5:54 am 02/28/2012

    Dartian says…

    —————–
    But it isn’t really positioned “between” them! In a bifurcating cladogram, you could change places of the branch that leads to Steno and the branch that leads to ((((Globicephala+Peponocephala)+Feresa)+Pseudorca)+Grampus) and still have the exact same tree. And Orcaella, in turn, is exactly equally closely related to either branch.
    —————–

    You’re confusing me. McGowen et al. (2006) show the following branching order: Orcaella, then Steno, then Grampus + ‘blackfish’. Whichever way you look at it, they showed Steno as being closer to Grampus + ‘blackfish’ than was Orcaella. Oh, wait a minute.. ok, I get it: you mean that the topology can be (Orcaella + ((Grampus + ‘blackfish’) + Steno)). Well, ok, my bad, Steno is not necessarily ‘between’ Grampus + ‘blackfish’ and Orcaella, but it’s still closer to the former than the latter.

    Darren

    Link to this
  15. 15. Dartian 6:31 am 02/28/2012

    Darren:
    “Steno is not necessarily ‘between’ Grampus + ‘blackfish’ and Orcaella”

    That “not necessarily” is an understatement; it is, in fact, logically impossible for Steno to be ‘between’ those two other clades (as recovered in McGowan et al‘s. analysis).

    it’s still closer to the former than the latter

    Yes, and so it must be (as per above).

    (Sorry to be making such a fuss about this, but I think this issue isn’t just semantics or hair-splitting; to the contrary, how to interpret phylogenetic trees is a matter of fundamental importance to any evolutionary biologist.)

    Link to this
  16. 16. David Marjanović 9:09 am 02/28/2012

    Rough-toothed dolphin (Steno bredanensis), photo by NOAA, from wikipedia. Sure doesn’t look like the other globicephalines… Richard Ellis said that it looks like an ichthyosaur.

    …Yeah. Where exactly did it leave its melon!?!?!

    It does have small eyes, though.

    More generally speaking, I’m not certain if it’s even theoretically possible for a species/clade to be truly phylogenetically ‘intermediate’ between two others (let’s ignore interspecific hybridization events which take place at the level of individuals).

    Intermediate? In an ancestor/descendant series? A species could be (depending on your species concept), a clade by definition couldn’t. Otherwise, what do you mean by “intermediate”?

    hard polytomies (assuming that such things ‘really’ exist)

    Apparently they do. Lots of Mediterranean lizards, 8 extant species IIRC, seem to have diverged simultaneously when the Mediterranean was flooded again.

    Of course, that’s a special case; it’s generally a safe assumption that any polytomy you encounter is soft = represents just a lack of information.

    Link to this
  17. 17. David Marjanović 9:10 am 02/28/2012

    If you just say “morphologically intermediate”, anything goes. But that may require sweeping any autapomorphies the taxon in question has under the carpet.

    Link to this
  18. 18. Heteromeles 9:52 am 02/28/2012

    As for an example of a hard polytomy…

    If memory serves, there’s a species of Polystichum fern that is the allotetraploid descendent of two extant diploid species of Polystichum. However, according to the genetic evidence, at least three independent hybridization events between the parental diploid species had given rise to the daughter tetraploid species in three separate locations.

    Unfortunately, my fern references are in storage, so I don’t have the paper reference readily available.

    Link to this
  19. 19. Boesse 1:05 pm 02/28/2012

    Hey Darren,

    Yes,that is certainly an issue – part of the problem is that not very many morphological characters have been generated for delphinids. They are, to be honest, the most frustrating group of cetaceans in general to work with – globicephalines in particular are the most disparate in terms of their morphology, and the easiest to work with because they have a relatively unique suite of characters to work with due to a number of factors involving rostral length/robustness, orbit robustness, tooth count/morphology. There are nearly zero morphologically useful characters that have been identified to really differentiate between non-globicephalines – in fact, in some cases it is extremely difficult to actually pick out individual species from skulls, particularly in the Delphinus-Stenella complex. For this reason, it will be very difficult to ever get Orcinus to stand apart from true globicephalines in an analysis as it exhibits so many globicephaline cranial features (large size, wide premaxillae, extremely large antorbital processes, low tooth count, etc.)

    The only other morphological analysis of globicephalines I know of is Bianucci (2005), and it only has 10 more characters and 12 taxa; most of these were used by Aguirre-Fernandez et al., and they eliminated ones which Protoglobicephala couldn’t be coded for. Either way, it shows the same pattern. I’ve got a pdf of Bianucci 2005 if you’d like it, just email me. And no, unfortunately, Paleontographica Italica isn’t online, which is too bad, because there are a great series of cetacean papers in there by Giovanni Bianucci and Michelangelo Bisconti.

    Unfortunately, as far as looking at rostrum length trends within delphinidae – this is really all we have to go with as pertains to morphological phylogenies. However, it fortunately means that there is plenty for us paleocetologists to work on. Regardless of the number of taxa/characters, I consider anyone who attempts to tackle a morphological phylogeny of delphinids a brave soul.

    Link to this
  20. 20. Dartian 2:11 am 02/29/2012

    David:
    In an ancestor/descendant series?

    No, specifically in a cladogram* (sorry if that wasn’t clear).

    * This cladogram, to be precise.

    what do you mean by “intermediate”?

    It was Darren who originally used the word; I was just pointing out that (ignoring interspecific hybrids, and with the possible exception of (hard) polytomies) no taxa can truly be said to be phylogenetically ‘intermediate’ or positioned ‘between’ others in a bifurcating cladogram.

    If you just say “morphologically intermediate”, anything goes.

    Yes, but that, of course, would be Something Completely Different. A chimpanzee may (perhaps!) be said to be morphologically intermediate between a gibbon and a human, but the chimpanzee most certainly isn’t (and, indeed, can’t be) phylogenetically intermediate between them.

    Link to this
  21. 21. Dartian 3:19 am 02/29/2012

    We should perhaps get this discussion back on topic:

    I was intrigued to learn that Risso’s dolphin is a cephalopod specialist. It is, of course, far from the only cetacean to specialise on this kind of prey; sperm whales and beaked whales come to mind. And it is striking how many of these odontocetes that mainly prey on cephalopods have reduced the number of their teeth. Sperm whales have lost their upper jaw teeth, many beaked whales are functionally toothless (some species have spectacular tusks, but these seem to be used only as weapons in intraspecific conflicts and not to capture/handle prey), and Risso’s dolphin has lost most of its teeth too.

    Is it actually actively disadvantageous (as opposed to merely unnecessary) for a cephalopod specialist to have teeth, I wonder? Ant-eating mammals tend to reduce/lose their teeth too, and this is probably (at least partly) related to the fact that formic acid is bad for the teeth. Could some similar selection factor be at play here? Is there something about cephalopod body composition that wears down mammalian teeth? Or is this too far-fetched an idea?

    Link to this
  22. 22. naishd 4:07 am 02/29/2012

    Dartian: I’ve read in the literature on ziphiids that loss of teeth is advantageous for cephalopod specialists since the teeth give the cephalopods something to grip to. This may be one of several contributory factors I suppose: another is that cephalopod specialists tend to use suction to get prey into the mouth, thereby making teeth somewhat (though not wholly) redundant in procuring prey. It is indeed intriguing that delphinids have convergently evolved their own ‘sperm whales’.

    Darren

    Link to this
  23. 23. Jerzy New 4:31 am 02/29/2012

    @naishd
    Thanks, I think it should be more known among the public who generally see dolphins as friendly, ethical etc.

    @David Marjanovic
    Polytomies should be regular, and relatively common in evolution.

    Speciation is supposed to take relatively long time, hundreds of generations, so there is enough time that two speciation events occassionally overlap. Also, factors supposed to often cause speciation – some environmental change splitting population like changing climate or this sea level rise – likely often split a widespread species into many subpopulations at the same time.

    It would be interesting to look at species like Alpine plants or ptarmigan which were isolated in many refugia after the last Ice Age. They are good candidates for polytomies and there is relatively precise information on the driving factor of isolation.

    Link to this
  24. 24. David Marjanović 10:49 am 02/29/2012

    cephalopod specialists tend to use suction to get prey into the mouth, thereby making teeth somewhat (though not wholly) redundant in procuring prey

    …while ichthyosaurs apparently were not suction feeders, which probably explains why most (but not all) of them kept their teeth, lots and lots and lots of teeth.

    Speciation is supposed to take relatively long time, hundreds of generations, so there is enough time that two speciation events occassionally overlap.

    That wouldn’t be a really hard polytomy, it would be two bifurcations with incomplete lineage sorting…

    Also, it’s very important which species concept you have in mind here. Here, you just mean “cladogenesis” by “speciation”, right?

    Link to this
  25. 25. Heteromeles 11:33 am 02/29/2012

    Speciation can happen very rapidly. All you need to do is get a breeding population to a new island, and that’s the start of the new species.

    In plants, all you need is mitotic failure in a bud, and that branch can no longer breed with the rest of the plant. If the flowers it produces can self-pollinate, though, it can produce reproductively isolated offspring. Or, as in orchids, all you need is a successful hybridization event. Since each orchid pollination event produces thousands of seeds, a single hybridization can lead to a new, reproductively isolated population, effectively a new species.

    My suspicion is that speciation looks like it happens slowly in the fossil record, because the critical isolating event is invisible, while the subsequent diverging changes are not. In plants, we probably get cryptic species all the time (cf California poppies, Eschscholzia californica), but most of them die out fairly quickly. This might happen in animals too.

    Link to this
  26. 26. Boesse 12:08 pm 02/29/2012

    David – there is actually a toothless ichthyosaur that is hypothesized to be a suction feeder:

    http://www.plosone.org/article/info:doi%2F10.1371%2Fjournal.pone.0019480

    With respect to tooth loss, it is a fairly common situation within the odontoceti: ziphiids mostly all have extremely reduced dentitions, physeterids and kogiids mostly lack upper teeth (fossil members of these clades are an exception), Monodon has lost most of its teeth, Odobenocetops has similarly lost most of its teeth, Grampus, and the bizarre Miocene eurhinodelphinid Vanbreenia has lost most of its teeth as well. Again, all of this is hypothesized to be related to suction feeding of one form or another. The pattern of tooth loss is pretty damn bizarre, and it seems that most of these taxa leave some sort of tusk behind – exceptions being Grampus, which could very well evolve towards total edentulousness within a couple more million years. Several of these taxa do appear to have some sort of social roles for these teeth as well – ziphiids, Physeter, and Monodon. This is also paralleled by the Pliocene walrus Valenictus, which lost all of its non-tusk teeth and was nearly edentulous, and like the modern walrus, a suction feeder (albeit for hard shelled mollusks).

    Darren, would you happen to have a reference on cephalopods ‘grabbing’ onto teeth, or at least a reference for that hypothesized loss of teeth?

    Link to this
  27. 27. Heteromeles 12:24 pm 02/29/2012

    How easy is it to see suction feeding in bones? As I understand it, whales primarily use their tongues, while fish and others use their jaws to generate the suction.

    How would ichthyosaurs do it? Or do we not have intact enough skulls to figure that out yet?

    Link to this
  28. 28. naishd 6:36 pm 02/29/2012

    Loving all these comments, thanks everyone. Yes, suction feeding has been proposed for the apparently short-snouted Shastasaurus shastasaurian ichthyosaurs of the Triassic.

    Bobby: with regard to the idea that tooth reduction might be advantageous for cephalopod-eaters because it reduces grip points for cephalopods, I’m pretty sure I’ve seen this a few times in papers on both ziphiids and sperm whales. I checked Heyning & Mead (1996), and on p. 9 we find (in a discussion of the rugose palate of Phocoenoides) “Such a palate would provide a non-skid surface which does not offer projections (i.e., teeth) upon which the squid’s tentacles can grasp and thus hinder the ingestion of the still live prey”.

    Heteromeles (comment 27): there are several fairly reliable indicators of a suction feeding habit in aquatic or amphibious tetrapods. They include large, robust hyoids involved in rapid (and often substantial) distension of the throat/depression of the floor of the mouth, enlarged retroarticular processes and associated hypertrophied musculature involved in rapid jaw opening, a snout shape that produces a small pressure wave when the mouth is opened/head is moved forward, a vaulted palate that allows rapid engulfing of prey/water, and tooth reduction/loss. A lot of neat work has been done on suction feeding in plethodontid salamanders and turtles – I’ve mentioned it when writing about placodonts but have never elaborated at length. Still planning to! These features are present in the suction-feeding ichthyosaurs. I had a sort of minor background role in that paper…

    Darren

    Ref – -

    Heyning, J. E. & Mead, J. G. 1996. Suction feeding in beaked whales: morphological and observational evidence. Natural History Museum of Los Angeles County, Contributions in Science 464, 1-12.

    Link to this
  29. 29. Heteromeles 9:44 am 03/1/2012

    Thanks Darren.

    Another question, if I may: just how useful are things like number of teeth per jaw in delineating species in this group? If jaws have been shortened and teeth have been lost numerous times independently, I’d guess that tooth number, if not tooth shape, would tend to be quite variable within species as well.

    Link to this
  30. 30. Hai~Ren 12:08 pm 03/2/2012

    There is another image of a dead Risso’s dolphin at this link: http://www.paulhiltonphotography.com/index.php/field-notes/41

    It’s a post about a practice that’s being carried out in Lombok in Indonesia, killing dolphins to be used as bait to catch sharks, which are then harvested especially for the shark fin trade.

    Link to this
  31. 31. Boesse 12:47 pm 03/2/2012

    Thanks Darren – that’s a paper I just never got around to getting through ILL for whatever reason.

    Heteromeles – yes, tooth # can be variable, but tooth counts are often used to identify stranded carcasses of globicephalines, and have been used as morphological characters in phylogenetic analyses of the group – a lower number of teeth is often used as a character supporting the Globicephalinae.

    Link to this
  32. 32. David Marjanović 3:01 pm 03/5/2012

    killing dolphins to be used as bait to catch sharks, which are then harvested especially for the shark fin trade

    *headdesk*
    *headdesk*
    *headdesk*
    *headdesk*

    Link to this
  33. 33. Dartian 7:02 am 03/6/2012

    I can’t let go of the subject of polytomies quite yet…

    David:
    Apparently they do. Lots of Mediterranean lizards, 8 extant species IIRC, seem to have diverged simultaneously

    But simultaneous splitting-off is not enough, is it? Surely, the three (or more) respective founding populations also have to be genetically identical? If they differ in this regard – even if only slightly – they will not form a real hard polytomy, as the interrelationships between these founding populations will then be unequal.

    To illustrate the above with a (deliberately) simple example: Let’s say we have three individuals – Darren, David, and Jerzy. They are all contemporary members of the same species, extant Homo sapiens – a species which, as it happens, is genetically quite uniform. And yet, one couldn’t correctly depict the interrelationships between Darren, David, and Jerzy as a hard polytomy (a hard trichotomy, in this case). Inevitably, of these three individuals, two will share a more recent last common ancestor and thus form a clade that excludes the third. It could be either
    ((Darren+David)+Jerzy), or
    ((Darren+Jerzy)+David), or
    ((David+Jerzy)+Darren).
    But, as far as I can see, there is no biologically realistic way that these three individuals could be equally closely related to each other. Hence, they do not form a hard polytomy. (Of course, one may perform a phylogenetic analysis of these three individuals that fails to resolve their true interrelationships. But such a result would be a soft polytomy, not a reflection of reality.)

    Now, as I said, that was a simple, or even a simplistic, example (being males, these individuals obviously couldn’t by themselves start new populations). But it did, I hope, convey my point; namely, that hard polytomies should be presumed to be quite uncommon under natural conditions, at least among sexually reproducing animals. I suppose that hard polytomies could happen if the source population is completely panmictic – but how often is that the case in the real world?

    Link to this
  34. 34. David Marjanović 7:40 am 03/6/2012

    But, as far as I can see, there is no biologically realistic way that these three individuals could be equally closely related to each other.

    On average, we could be – with different genes having different phylogenetic trees. The simplest example is mtDNA vs. the Y chromosome.

    Naturally, this is even easier when we consider whole populations instead of individuals.

    Link to this

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