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I always get excited when Paul Sereno publishes a paper in PLoS ONE and today is one such day – his third paper in this journal within a span of less than a year (the first was the paper with detailed description of Nigersaurus and the second was the article on Green Sahara cemeteries). Today’s paper is also the second time PLoS ONE publishes a taxonomy paper, i.e., a monograph that describes a new species:

Evidence for Avian Intrathoracic Air Sacs in a New Predatory Dinosaur from Argentina:

Background

Living birds possess a unique heterogeneous pulmonary system composed of a rigid, dorsally-anchored lung and several compliant air sacs that operate as bellows, driving inspired air through the lung. Evidence from the fossil record for the origin and evolution of this system is extremely limited, because lungs do not fossilize and because the bellow-like air sacs in living birds only rarely penetrate (pneumatize) skeletal bone and thus leave a record of their presence.

Methodology/Principal Findings

We describe a new predatory dinosaur from Upper Cretaceous rocks in Argentina, Aerosteon riocoloradensis gen. et sp. nov., that exhibits extreme pneumatization of skeletal bone, including pneumatic hollowing of the furcula and ilium. In living birds, these two bones are pneumatized by diverticulae of air sacs (clavicular, abdominal) that are involved in pulmonary ventilation. We also describe several pneumatized gastralia (“stomach ribs”), which suggest that diverticulae of the air sac system were present in surface tissues of the thorax.

Conclusions/Significance

We present a four-phase model for the evolution of avian air sacs and costosternal-driven lung ventilation based on the known fossil record of theropod dinosaurs and osteological correlates in extant birds:

(1) Phase I–Elaboration of paraxial cervical air sacs in basal theropods no later than the earliest Late Triassic.

(2) Phase II–Differentiation of avian ventilatory air sacs, including both cranial (clavicular air sac) and caudal (abdominal air sac) divisions, in basal tetanurans during the Jurassic. A heterogeneous respiratory tract with compliant air sacs, in turn, suggests the presence of rigid, dorsally attached lungs with flow-through ventilation.

(3) Phase III–Evolution of a primitive costosternal pump in maniraptoriform theropods before the close of the Jurassic.

(4) Phase IV–Evolution of an advanced costosternal pump in maniraptoran theropods before the close of the Jurassic.

In addition, we conclude:

(5) The advent of avian unidirectional lung ventilation is not possible to pinpoint, as osteological correlates have yet to be identified for uni- or bidirectional lung ventilation.

(6) The origin and evolution of avian air sacs may have been driven by one or more of the following three factors: flow-through lung ventilation, locomotory balance, and/or thermal regulation.

Wow! Read the whole thing!

For more, read Greg Laden’s thoughts.

Comments

  1. #1 Greg Laden
    September 29, 2008

    This is an excellent example of PLoS One being a very high end journal, I’d say.

  2. #2 Monado
    September 29, 2008

    Nice! Altho’ I do think it’s funny that Paul Serano is styled “Explorer in Residence.” You’d think that the National Geographic Society would want him out on the road: “Explorer at Large”, perhaps?

  3. #3 Sven DiMilo
    September 29, 2008

    Looks excellent…thanks for the tip. Paleophysiology is fraught with wishful thinking, but this scenario looks properly qualified.

  4. #4 Aerosteoff
    October 6, 2008

    For a different perspective on this paper by someone who is a pneumaticity expert, see these posts on SV-POW:

    The Aerosteon saga, Part 1: Introduction and background

    The Aerosteon saga, Part 2: Overinflation and undercitation

  5. #5 Andy
    October 6, 2008

    But, see this link presenting some problems with the Sereno et al. paper. . .their case is not as “air-tight” as it might seem at first: The Aerosteon Saga, Part 1 and The Aerosteon Saga, Part 2

    Granted, the blog post is written by one of the authors whose interpretations differ from that of the Aerosteon authors. . .but, having read many of the relevant papers myself, I think Wedel has some very good points.

  6. #6 Coturnix
    October 6, 2008

    Yes, I read the first part the other day and will the second part now. Interesting criticism. Thank you.

  7. #7 Sceptic
    October 7, 2008

    Is part of the reson he publishes there so much that is is also one of the editors of PLOS1? Not to mention the fact that this paper was accepted just 11 days after submission. A random survey of a handful of other papers on the PLOS1 database suggest a normal review time of 1-3 months, and the authors thank only a single person for comments on the manuscript and make no mention of referees. (I am not suggesting this was *not* peer reviewed).

    One should have the option to publish in a journal for which one acts as an editor and rapid reviews do happen. However, given the criticism this paper has already come in for it does not look good when the author is both an editor and appears blessed with an incredibly rapid and favourable review.