Ventastega fills another gap in tetrapod evolution

Tiktaalik was a tetrapod with legs that was still mostly lobe-finned fish. Ventastega is a tetrapod with legs that is closer to earlier lobe-finned fish like Acathostega. Here’s a bit from the Nature News:

fossil tetrapod Ventastega curonicaFossils of a four-legged fish have filled in our understanding of the evolution of land-based vertebrates.

Initially described in 1994, early specimens of Ventastega curonica were fragmented, and hard to interpret. New examples from Latvia have now allowed researchers to reconstruct the head, shoulders and part of the pelvis of the ugly looking beast (press release, research paper in Nature).

The editor’s summary in Nature notes that the new work shows Ventastega has the skull shape of an early tetrapod but the proportions of a fish. It provides new insights in the evolution of early land-dwelling vertebrates (called tetrapods) some 370 million years ago in the Late Devonian period.

“From a distance, it would have looked like an alligator,” says study author Per Ahlberg, of Uppsala University in Sweden (BBC). “But closer up, you would have noticed a real tail fin at the back end, a gill flap at the side of the head; also lines of pores snaking across head and body. In terms of construction, it had already undergone most of the changes from fish towards land animal, but in terms of lifestyle you are still looking at an animal that is habitually aquatic.”

tetrapod vossil Ventastega

Ahlberg speculates that it was crawling around on sandy banks and eating stranded fish in tidal creeks (AP).

Ted Daeschler, paleontologist at the Academy of Natural Sciences in Philadelphia, explains to National Geographic that although we have a general outline of the transition between fish and tetrapods there’s a lot we don’t know. It’s like building a house, he says: “We’ve got the frame built. We know what the rooms are shaped like. But we haven’t put in the electricity, installed the lamps, or put Sheetrock on the walls.”

Picture upper: Philip Renne and Per Ahlberg
Picture lower: Ventastega in side view / Per Ahlberg

Here’s the abstract from Thursday’s Nature:

Nature 453, 1199-1204 (26 June 2008) | doi:10.1038/nature06991; Received 22 November 2007; Accepted 9 April 2008

Ventastega curonica and the origin of tetrapod morphology

Per E. Ahlberg1, Jennifer A. Clack2, Ervi macrns Luks caronevic carons3, Henning Blom1 & Ivars Zupincedils caron4

  1. Subdepartment of Evolutionary Organismal Biology, Department of Physiology and Developmental Biology, Uppsala University, Norbyvägen 18A, 752 36 Uppsala, Sweden
  2. University Museum of Zoology, Cambridge, Downing Street, Cambridge CB2 3EJ, UK
  3. Department of Geology, University of Latvia, Rainis Blvd 19, Riga LV-1586, Latvia
  4. Natural History Museum of Latvia, K. Barona Str. 4, Riga LV-1712, Latvia

Correspondence to: Per E. Ahlberg1 Correspondence and requests for materials should be addressed to P.E.A. (Email: per.ahlberg@ebc.uu.se).

The gap in our understanding of the evolutionary transition from fish to tetrapod is beginning to close thanks to the discovery of new intermediate forms such as Tiktaalik roseae. Here we narrow it further by presenting the skull, exceptionally preserved braincase, shoulder girdle and partial pelvis of Ventastega curonica from the Late Devonian of Latvia, a transitional intermediate form between the ‘elpistostegids’ Panderichthys and Tiktaalik and the Devonian tetrapods (limbed vertebrates) Acanthostega and Ichthyostega. Ventastega is the most primitive Devonian tetrapod represented by extensive remains, and casts light on a part of the phylogeny otherwise only represented by fragmentary taxa: it illuminates the origin of principal tetrapod structures and the extent of morphological diversity among the transitional forms.

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Once you get the Emperor Workstation, you can sit in ergonomic comfort with a different task on each screen. In fact, you’ll hardly ever have to stop working.

Hat tip to Jason Rosenhouse at Evolutionblog.

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This is a reduced image of the one from Core77 design.

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Romanian child will get abortion

An 11-year-old, pregnant by rape, will be allowed to have an abortion in Romania. This solution seems obvious, for children shouldn’t be forced to bear children. But the church opposes this abortion. Maternal death rates have plummeted since abortion was legalized, but this girl is “14 weeks” pregnant–over the limit for Romania. She probably didn’t realize she was pregnant until at least “10 weeks” pregnant — about when morning sickness starts. I added the quotation marks because pregnancy is dated from the first day of the last menstrual period, so officially you are two weeks pregnant when you conceive.

(CNN) — A Romanian government committee has decided to allow a pregnant 11-year-old who was raped by her teenage uncle to have an abortion, a government spokesman said Friday.

The girl is 21 weeks pregnant — too far along to have an abortion in Romania, where the limit is 14 weeks unless the pregnancy poses problems for the mother’s health, said the spokesman, who asked not to be named.

The girl’s parents had said they would take their daughter to Britain for an abortion if the committee did not allow her to have one in Romania. Abortions are legal in Britain up to 24 weeks.

It was unclear whether the parents would still take the girl to Britain following the committee’s decision, reached late Thursday.

Church groups have opposed an abortion for the girl, the government spokesman said. The Romanian Orthodox Church has urged the girl to keep the baby, and has said it will take care of the baby if the family wants to give it up for adoption, he said.

The uncle who raped the girl has since disappeared, the Romanian Health Ministry said. Media reports say the uncle is age 19.

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