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This is where I post various musings about wildlife and ecology, observations of interesting species (often invertebrates)
and bits of research that grab my attention. As well as blogging, I undertake professional ecological & wildlife surveys
covering invertebrates, plants, birds, reptiles, amphibians and some mammals, plus habitat assessment and management
advice
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Monday, 11 March 2013

Cretaceous Crato creature 2

Though I do look at a lot of invertebrates, I rarely delve into palaeontology - however, a little while ago I did look at a bug from the Crato Formation (about 110-125 myo) in Brazil. I recently went shopping online again and found another one listed only as an 'insect' and not at all expensive, so (as the images looked fine) I decided to go for it and see if I could identify it myself. This is what appeared:

My 'new' Cretaceous Crato insect
It is by no means a large insect - the body is about 12mm long, the cerci (or 'tails') about 15mm if straightened, and the wingspan around 18mm. Using Bechly (2007), it didn't take long to determine that this is a mayfly, an adult or almost-mature 'subimago', probably of the family Leptophlebiidae. Apparently it is found reasonably often, but its taxonomic position is unclear - it may even be in a different family and is known simply as 'species 1'. So, that's as far as my identification can go - basically, it's a mayfly but beyond that nobody really knows. However, this doesn't mean its features can't be examined more closely...

Cretaceous mayfly: Leptophlebiidae (?) sp. 1
The head, thorax (orange and fairly uniform) and abdomen (speckled with pale pimples) can be clearly differentiated and four of the legs are visible, indicated by green arrows. The abdominal segments and midline, though slightly deformed are also visible (see the drawing below) as are the large forewings. The dark line extending top-left may be another leg - it's certainly about the right size.

Right forewing of Leptophlebiidae (?) sp. 1
The front margin of the wing is well preserved, along with sections of some of the veins radiating from the base, and some areas of the wing membrane itself. Not bad for its age... I think the outline suggested here is quite accurate as the shape is similar to other specimens, though maybe a little of the hind edge is missing.

The pair of long cerci, typical of this species (well, taxon - it might be one of several similar species) - note the thickened bases.
So, having investigated the main features, I decided to follow the methodology of other palaeontologists and produce a line drawing to try to elucidate the detail without the distraction of mineral colours and textures - these are useful when looking at some features, but a hindrance for others. By photographing, printing, tracing and scanning, this is what I came up with:

Line drawing of my specimen of Leptophlebiidae (?) sp. 1
Personally, I'm quite happy with this - although the wing membranes (for example) are lost here, the body segments are a little clearer and I think a sense of the overall level of preservation is clear e.g. the slight fragmentation of the cerci. Such specimens are generally given a catalogue number including an abbreviation of the museum they are in e.g. NHM 23438 would be specimen 23438 in London's Natural History Museum; maybe this mayfly should be DSH 00002, the second fossil insect in my collection of curios...

To finish, it's worth noting that the Leptophlebiidae are still around - there are about 2000 species worldwide, including 6 in Britain, though they have 3 cerci (one reason why the species here is of uncertain family), and the larvae have forked gills on their abdomens giving them their common North American name of 'prong-gilled mayflies'.

Reference

Bechly, G. (2007). Insects of the Crato Formation. In: Martill, D.M., Bechly, G. & Loveridge, R.F. (eds.). The Crato Fossil Beds of Brazil: Window into an Ancient World, Cambridge UP, pp. 142-426.

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