I had such helpful participation with my first fossil ID request that I thought I would go to the well again. This one is not so enigmatic as the first—it is clearly an insect, but it’s the only insect fossil among the batch that I haven’t settled on at least an order-level identification. Again, this is one of a set of 20 fossils loaned to me by a local collector for photographs and possible identifications, all coming from the Green River Formation in Colorado and dating back to the early to mid-Eocene (45–50 mya).
The label for this fossil indicates “Planthopper; Homoptera; Fulgoridae”; however, the short, robust legs and overall gestalt do not look right for either a planthopper or really any of the other hemipteran groups. What I see is an indistinct (mandibulate?) head, a distinct and well-developed pronotum, mes0- and metathoracic segments that are not nearly as heavily sclerotized as the pronotum but also lacking any sign of wings, a distinctly segmented abdomen with 9 or 10 segments, and short robust legs. I’m thinking an apterous/brachypterous coleopteran (Staphylinidae?) or a wingless member of one of the orthopteroid orders (although size alone excludes many of the latter—at more than 11 mm in length it is too large for something like Zoraptera). At first I thought the extension near the apex of the abdomen was a cercus, but I now think this is part of the piece of debris over the abdomen as there is no evidence of a cercus on the left side—another knock against something orthopteroid. Still, the lack of any trace of elytra—however shortened—keeps me from fully endorsing Coleoptera. Okay, so what do you guys think?
Copyright © Ted C. MacRae 2012
22 thoughts on “Beetle, orthop or something else?”
My immediate impression is Stenopelmatidae. Don’t know if that makes any sense.
Keeping this simple Ted, to me it looks like a Bess Beetle without elytra’s. Perhaps being underground would not require them during this time..? Very cool and obviously an insect!! Keep em coming.
It looks to me like an Isopteran, with the head indistinct or missing. The relatively short legs would seem to rule out Orthoptera.
I like Charley’s suggestion. It looks like there might even be a trace of the left cercus. On the other hand, the head seems rather too small.
Ted – Olivier B�thoux would like to see a photo of the fossil with some alcohol spread on top of it. D
Hi David – who is Olivier “B�thoux”, and what would doing this show? Just any alcohol?
Hi Ted – Looks like this post crept under my radar! I too would like to see a shot of this taken under ethanol (70-80%) as it will enhance the contrast and help make lightly mineralized structures more visible. The specimen is rather poorly preserved and the legs are clearly incomplete. Nevertheless, it does look orthopteran to me with the morphology of the pronotum consistent with an as yet undescribed gryllid that is fairly common in the Green River Fm (we eagerly await Gorochov’s monograph on the fauna!).
Hi Sam – okay I’ll take an photo under ethanol. Can I send you the high-rez image?
I will feel profoundly vindicated if it turns out to be an orthopteran!
Sure thing – you have my e-mail address.
In general, 11 mm is too small for several of the suggestions and too big for the other. It looks most to me like a wingless Dermapteran (earwig) but with the abdominal apex damaged. Or it could just be a Rorschach splotch. 😉
Ignoring the apparent pronotum, rest of fossil looks a lot like an dragonfly nymph. Not saying its the case here, but one needs to be aware of possibility of parts from two creatures being compressed together when considering ID options.
Five insect orders suggested so far (Orthoptera, Coleoptera, Isoptera, Dermaptera and Odonata). Glad to see my indecision being validated!
What if the “pronotum” is actually the head?
The “cerci” appears to me to be a horseshoe shaped reminant of something else, and not necessarily a part of the insect. My first impression (assuming that the specimen is intact) was Coleoptera: Staphylinidae. It would be interesting to see the opposing piece of rock and what is attached to it.
And believe me when I say that I didn’t read your assessment before typing the above! Great minds…. 🙂
Might as well up the ordinal tally – reminds me of a Zoraptera
I thought about that, but an 11mm zorapteran would be quite extraordinary!
I’m registering a vote for the Isoptera, it was my initial thought when I saw the photo.
My thoughts in order were Isoptera, then Dermaptera, then Staphylinid or similar.
And I will support Morgan and Mark. This looks like a termite to me.
I too could easily go with Isoptera, but I’m also awaiting the opinion of a certain someone who is especially knowledgable about fossil insects. We’ll see what they have to say. 🙂