Here’s a very strange fossil from the Chengjiang Lagerstätte, an early Cambrian fossil bed from 525 million years ago. It’s a collection of Waptia-like arthropods, nothing unusual there; these are ancient creatures that look rather like headless shrimp. What’s weird about it is the way the individuals are locked together in a daisy chain, with the telson (tail piece) of each individual stuck into the carapace of the animal behind. It’s not just a fluke, either — they have 22 fossil chains, and just one animal all by its lonesome.

(Click for larger image)
Waptia-like arthropod, Lower Cambrian, Haikou, Yunnan. (A) Individual with twisted abdomen, part of chain, Yunnan Key Laboratory for Palaeontology, YKLP 11020a. (B) Chain, about 20 individuals, various dorsoventral-lateral orientations, composite image (joined at cpt/p arrow), YKLP 11020a and YKLP 11020b. (C) Individual linked to carapace behind, lateral view, part of chain of nine individuals, YKLP 11021. (D) Isolated individual, subventral view, YKLP 11019. (E to G) Reconstruction shown in dorsal, ventral, and right lateral views, respectively. Scale bars in (A), (C), and (D) indicate 1 mm; in (B) and (E) to (G), 5 mm. b, s, and t indicate bent, stretched, and telescoped individuals, respectively; cpt, counterpart; f, facing direction; p, part; and tw, twisted.

They do not look like animals that were constrained in a burrow, or that were crawling over the surface. Rather, they had been swimming together in a chain at death, and the whole chain fell to the sea bed, bending and kinking but still remaining firmly locked together.

Why were they doing this? My first thought was of sex; everyone knows how dragonflies and damselflies lock together for mating, but of course that would predict pairs of individuals, not 20 at a time. It also reminded me of the Drosophila mutant fruitless, in which male flies court other male flies, and they spontaneously form conga lines in the culture bottles. That’s also unlikely, since that kind of behavior doesn’t lead to a consistent pattern of successful reproduction, but maybe if these animals were hermaphroditic, it might work. It’s not a behavior that any modern arthropods show, however.

The authors consider the possibility it is a feeding strategy, but that’s even worse: they’re locked basically mouth to anus, which would mean the fellow at the end of the line gets a very unpleasant diet. They conclude that the most likely explanation is that this represents a migratory behavior, perhaps involved in daily vertical migration. It may have been that strings of these animals would link up and paddle together to move to new feeding sites, where they separated and dispersed until the time came to move elsewhere.

Hou X-G, Siveter DJ, Aldridge RJ, Siveter DJ (2008) Collective Behavior in an Early Cambrian Arthropod. Science 322(5899):224.

Check it out: it’s yet another transitional form, a 92 million year old snake with two hindlimbs. Cool! Just last week I was told that none of these things exist.

It means “devil toad,” and it was a 10 pound monster that lived 70 million years ago, in what is now Madagascar. It’s huge, and judging by its living cousins, was a voracious predator. If it were alive today, it would probably be eating your cats and puppies.

In other words, this was an awesome toad, and I wish I had one for a pet.

Here’s what it looks like, with some very large extant toads for comparison.

Beelzebufo ampinga, Late Cretaceous of Madagascar. (A) Skull
reconstruction showing parts preserved (white areas, Left) and distribution of
pit-and-ridge ornament (stippling, Right). (B) Skeletal reconstruction and
inferred body outline of average-sized (skull width, 200 mm; SVL, 425 mm)
adult female B. ampinga based mainly on Lepidobatrachus asper. White
areas indicate parts represented by fossil specimens. For size comparison,
dorsal view silhouettes of Ceratophrys aurita (the largest extant ceratophryine) (C), and Mantidactylus guttulatus (the largest extant Malagasy frog) (D),
are shown. cp, crista parotica; fm, foramen magnum; frp, frontoparietal; mx,
maxilla; n, nasal; pmx, premaxilla; qj, quadratojugal; qu, quadrate; sq, squamosal. (Scale bars: 50 mm.)

There are some biogeographical puzzles associated with this beast. It’s found in Madagascar, but it’s closest extant relatives are South American…and since frogs and toads do a poor job of crossing salt water, that implies the existence of land bridges between those continents around the Cretaceous. It’s not a major puzzle, though, although some of the news reports I’ve seen play up the concern, as if it were a significant controversy. As the authors explain,

We suggest that extant ceratophryines are remnants
of a Gondwanan hyloid clade that once ranged from at least
South America to Indo-Madagascar. Whether this clade was
more broadly distributed and on which Gondwanan landmass it
originated cannot be determined on current evidence. However,
as the Late Cretaceous fauna of the Maevarano Fm,
including its ceratophryine anuran, bears little resemblance to
that of modern Madagascar, major biotic changes clearly occurred on the island in the intervening period. When and how the ancestors of the endemic mantellid and microhylid anurans arrived on Madagascar remains controversial,
but there is general agreement that these frogs did not diversify
significantly until the Paleogene. Their radiation
has been linked, at least in part, to the expansion of rainforests,
but may also have been facilitated by the extinction of archaic
faunal elements, including ceratophryines.

It was a diverse, widespread group once upon a time, and it’s not at all challenging to report that the continents have shifted in 70 million years. It’s just very cool that anurans achieved the status of charismatic megafauna^*, once upon a time.

^*For a generous definition of “mega”.

Evans SE, Jones MEH, Krause DW (2008) A giant frog with South American affinities from the Late Cretaceous of Madagascar. Proc Nat Acad Sci USA 105(8):2951-2956.

The capybara is the current champion for rodents of unusual size — it weighs about 60kg (about 130 pounds); another large rodent is the pakarana, which weighs about a quarter of that. Either one is far too much rattiness for most people to want hanging around.

Now there’s another king of the rodents: Josephoartigasia monesi, which is estimated to have tipped the scales at about 1000kg, over a ton. Don’t worry about getting bigger rat traps; these beasties have been extinct for perhaps 2 million years. I’ve put a few pictures from the paper describing this new species below the fold.

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