From the Collections Room (Pseudopolycentropodes)

Psuedopolycentropodes virginicusHolotypeVMNH 49566Solite QuarryCascade, VAChristina has been making steady progress photographing the Solite insects, a project that is being paid for by the National Science Foundation. Waterbugs, likely from the family Notonectidae, are probably the most common insects at the site, but the insects are actually very diverse and we have examples from a lot of other groups, such as the specimen shown above.

This is the holotype specimen of Pseudopolycentropodes virginicus, a relative of the scorpionflies, and one of the rarest Solite insects. There are only three known specimens of this species, one at VMNH and two at the Yale Peabody Museum. The scale bar is 5 mm, so the body of this insect is only about 3 mm long. Here’s the counterpart of the same specimen:

Psuedopolycentropodes virginicus Holotype VMNH 49566 Solite Quarry Cascade, VA

 

The scorpionflies are not true flies (which are in the order Diptera), but are instead in the order Mecoptera; one of the easily identifiable differences is that dipterans only have two wings, while mecopterans have four. There are several hundred living scorpionfly species, including Panorpa virginica (below, from the VMNH collection):

2014-04-25c

 

Pseudopolycentropodes provides a good example of the exceptional preservation in the the Solite insect bed. Some of the visible features include tiny hairs along the back that are only a fraction of a millimeter in diameter:

Psuedopolycentropodes virginicus Holotype VMNH 49566 Solite Quarry Cascade, VA

There are also tibial spurs on the legs (the spikes sticking out from each side of the leg below, which are also visible in the Panorpa photograph):

Psuedopolycentropodes virginicus Holotype VMNH 49566 Solite Quarry Cascade, VA

Pseudopolycentropodes is a member of the extinct family Pseudopolycentropodidae, members of which are only known from the Mesozoic Era. This family has an interesting geographic distribution, in that they are known almost exclusively from Europe and Asia. In fact, the three Solite specimens of Pseudopolycentropodes are the only known occurrences of this family outside of Eurasia. Even though they’re known from Triassic deposits in North America, France, and Kyrgyzstan, they have not turned up the insect-rich Triassic deposits from Australia and South Africa (Grimaldi et al. 2005), meaning that they’re restricted to Laurasia (the northern continents) and are absent from Gondwana (the southern continents + India).

The surprising thing about this distribution is that in the Late Triassic Pangea was only starting to rift apart, so Laurasia and Gondwana were still connected to each other. But even with this land connection it seems that pseudopolycentropodids were not able to move from Laurasia into Gondwana. We see this pattern repeated (or nearly so) in other groups as well, such as the wind-blown seed Fraxinopsis, which is widespread in Gondwana but is known from only one Laurasia locality (which happens to be the Solite Quarry). So it seems that, even though Laurasia and Gondwana were connected in the Triassic, there were still significant barriers making it difficult for many organisms to disperse across both regions.

But I have to say, in addition to the beautiful micro-detail in the type specimen and the interesting paleobiogeographic issues, I love the fact that 3-mm-long Pseudopolycentropodes virginicus has a 32-character, 12-syllable name!

Reference:

Grimaldi, D., Junfeng Z., Fraser, N., and Rasnistyn, A. 2005. Revision of the bizarre Mesozoic scorpionflies in the Pseudopolycentropodidae (Mecopteroidea). Insect Systematics and Evolution 36:443-458.

Advertisements
This entry was posted in From the Collections Room, Newark Supergroup. Bookmark the permalink.

Leave a Reply

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

WordPress.com Logo

You are commenting using your WordPress.com 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