Science Literature

Recent years have seen significant advances in our knowledge of the biology of extinct placoderm fish. These animals are now regarded as the earliest vertebrates capable of live birth. Embryos have been found inside pregnant fish alongside evidence for the presence of an umbilical cord (go here and here). The latest reported find concerns the male reproductive organ necessary for internal fertilisation.

The females of Incisoscutum ritchiei bore live young following internal fertilisation (source here)

The background to the discovery of the male organ is interesting in its own right. Males have "penis-like pelvic claspers similar to those found in fossil Ptyctodontida (a group of unarmoured placoderms) and in sharks".
The fossil revealing this organ was found in 2001, but the pelvic clasper was labelled as the pelvic girdle. Second author Kate Trinajstic explained

"at the time, we didn't realize that live births were possible. [. . .] [E]arlier this year [. . . we] looked at this specimen with a new set of eyes. As soon as [Per Ahlberg] got it under a high power microscope, we both realised we had found the missing clasper".

This provides a striking example of human factors affecting the outworking of the scientific method. We are familiar with the idea of scientists gathering data in order to test hypotheses, but much less aware of the way worldviews and paradigms affect what we see as data and what hypotheses we consider to be worthy of testing. When placoderms were considered "primitive", no one was looking for unborn embryos or for the means to achieve internal fertilisation. This was not a hypothesis entertained by the researchers. Even when they looked at a male clasper, they did not recognise what it was. However, once internal fertilisation and live births became accepted (the new paradigm for placoderm biology), the researchers were alerted to new possible explanations of fossil material. Per Ahlberg is quoted as saying: "It provides a pedigree of nearly 400 million years for the "advanced" and seemingly specialized reproductive biology of modern sharks".

Design thinking is like this. Once one accepts the legitimacy of making design inferences within science, the data looks rather different. With the new paradigm, evidences of design appear to be pervasive. Evolutionary presumptions about the "primitiveness" of so-called stem organisms no longer seem coherent. Complex specified information diagnostic of design can be found everywhere we look.

Pelvic claspers confirm chondrichthyan-like internal fertilization in arthrodires
Per Ahlberg, Kate Trinajstic, Zerina Johanson & John Long
Nature 460, 888-889 (13 August 2009) | doi:10.1038/nature08176

Recent finds demonstrate that internal fertilization and viviparity (live birth) were more widespread in the Placodermi, an extinct group of armoured fishes, than was previously realized. Placoderms represent the sister group of the crown group jawed vertebrates (Gnathostomata), making their mode(s) of reproduction potentially informative about primitive gnathostome conditions. An ossified pelvic fin basipterygium discovered in the arthrodire Incisoscutum ritchiei was hypothesized to be identical in males and females, with males presumed to have an additional cartilaginous element or series forming a clasper. Here we report the discovery of a completely ossified pelvic clasper in Incisoscutum ritchiei (WAM 03.3.28) which shows that this interpretation was incorrect: the basipterygium described previously is in fact unique to females. The male clasper is a slender rod attached to a square basal plate that articulates directly with the pelvis. It carries a small cap of dermal bone covered in denticles and small hooks that may be homologous with the much larger dermal component of the ptyctodont clasper.

See also:

Abstractions, Nature 460, 780 (13 August 2009) | doi:10.1038/7257780b

Sharks: Missing Piece Of Fossil Puzzle Found, ScienceDaily (July 14, 2009)