CURRENT BIRD-ORIGIN THEORIES:
NAME OF THEORY: Feduccia's; (Martin & ...); Birds are not Dinosaurs; BAND
ORIGINATORS: This was the generally accepted theory prior to the discovery of Deinonychus and John Ostrom's work on it. Now believed by Alan Feduccia, Larry Martin, Rubin, Oregon State Group, ...
TIME OF ORIGIN OF BIRDS: Triassic (presumably, since no suitable thecodonts reached Jurassic)
IMMEDIATE ANCESTOR OF BIRDS: Unknown thecodont (precursor to dinos); something a bit like Protoavis.
TIME OF FIRST FEATHER: ?
EXTINCT FEATHERED GROUPS: Believes Protarchaeopteryx and Caudipteryx to be birds; at least some supporters of this theory say Sinosauropteryx's fibrous fringe is collagen fibres under the skin, so they probably currently admit of no non-birds with fur/feathers. It will be interesting to see what the theory has to say about furred/feathered therizinosaurs, deinonychosaurs, etc, as and when they appear.
WEAKNESSES: Counts all the remarkable similarities between bird-like dinos and birds as parallel evolution. Not supported by cladistics. Cannot explain absence of early birds from typical aquatic pterosaur-bearing deposits of the J.
STRENGTHS: Theory once had "Most Favoured Theory" status; Quite a few famous people, particularly bird experts, still believe it; News and other media still haven't discovered its rapidly waning popularity amongst dino community; Considered by BAMM theorists to be safely thwarted, it is handy to trot out if one has to mention a token alternative theory to one's own, without the risk of growing numbers of people saying "But that's better than your theory!" For the latter two reasons, still given enormous coverage.
PREDICTIONS: Thecodont-bird missing link(s) to be found. [This kind of creature - a bit Protoavis-like - is expected by most theories]. BAND though might perhaps predict a rather less dino-like specimen. Also presumably predicts early forms of Cretaceous maniraptorans pre-Archae.
CHANGES NEEDED FOR CONVERSION TO 2F: Pre-Archae, very little change required, just that bird line probably came from early dino, not thecodont... though 2F officially says nothing much about pre-Archae, except no flyable feathers. Post-Archae, 2F agrees with BAND in that Archae did not arise FROM K manis; Change to belief in reverse arrangement required.
EVIDENCE REQUIRED FOR SUCH CHANGES: Clear lineage from very early dinos to late Triassic ancestor of Archae (may never be found); forms intermediate between Archae and early K manis (either direction would kill BAND) - therefore, after good examples of Rahonavis (with ribs), BAND should lie down.
GENERAL COMMENTS: Despite lacking support amongst dino folk, main proponents argue energetically that bird-like dinos were cold blooded and had reptilian lungs. Greg Paul likes to take them on over this. [see Dinolist passim] In fact he seems to put more effort into arguing against BAND than BAMM. Rubin wrote rather convincing paper ### suggesting Archae was cold-blooded. Group seems to dislike the idea that dinos were warm-blooded, and suggest that the Sinosauropteryx fossil's fluffy border was not fur/protofeathers but collagen fibres, of the type found in the frills of lizards and seasnakes. (They are also suggesting/pointing out that the supposed fur of the pterosaur Sordes pilosus is collagen fibres.)
The evidence that perhaps the three surviving fingers of birds correspond to digits II,III,IV of the original thecodont/early dino five-fingered hand instead of the I,II,III of dinos like Allosaurus, suits their position well.
Actually, like 2F, no particular pre-Archae bird ancestor is claimed, except thecodonts are preferred to dinos. If that could be changed, and ancestry of K manis accepted, it would be 2F.
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NAME OF THEORY: "Birds are Modified Maniraptorans" BAMM (Called "Birds are Dinosaur Descendants (BADD) by George Olshevsky)
ORIGINATORS: Sprang from the discovery of the birdliness of Deinonychus by John Ostrom, who said it may be closely related to birds. (See Ostrom's famous monograph on Deinonychus.)
TIME OF ORIGIN OF BIRDS: Late Jurassic
IMMEDIATE ANCESTOR OF BIRDS: Small theropods (the meat eating dinosaurs), eg maniraptorans such as Deinonychus.
TIME OF FIRST FEATHER: Any time pre-Archaeopteryx
EXTINCT FEATHERED GROUPS: Certain unspecified non-avian dinosaurs.
WEAKNESSES: Cannot explain evolution of obviously flight-oriented feathers worn by Caudipteryx & Protarchaeopteryx etc, not birds in this theory. Cannot explain absence of early forms of Cretaceous maniraptorans pre-Archae. Account of evolution of flight-oriented features of non-flying maniraptorans not very convincing. Tends to be associated with "Ground up" theory of flight evolution (as opposed to Bird evolution) though not irretrieveably. Doesn't categorise enough early birdlike types as ex-flying (only Alvarezsaurs).
STRENGTHS: Currently "Most Favoured Theory" - believed by most dinopeople at all levels; supported by cladistics. Recognised by media.
PREDICTIONS: Pre-Archae early forms of Cretaceous maniraptorans. Also, only predicts ONE version intermediate between birds and dinos.
CHANGES NEEDED FOR CONVERSION TO 2F: Manis already considered relatives of birds, only direction of relationship needs changing. First feather at time of Archae.
EVIDENCE REQUIRED FOR SUCH CHANGES: All pre-Archae types found without feathers; all (or most) K manis with feathers; clearly flightless or flying K manis
GENERAL COMMENTS: Confidence and numbers of supporters now so strong, partly due to support by cladistics, that expositions often become blatantly crass, and also fail to accept their theory is just a theory. If enough dino-bird fossil evidence arrives to prove BAMM wrong, this will be a very bad day for current conventional palaeontology and its supporters, and also for cladistics, for which it is likely to provide the sole convincing test.
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NAME OF THEORY: Secondary Flightlessness (2F)
ORIGINATORS: Gregory S. Paul, notably in his 1988 book "Predatory Dinosaurs of the World" (Now out of print, but not to worry...he hasn't given up authorship!) All further details below refer to the writer's (JJ's) personal interpretation.
TIME OF ORIGIN OF BIRDS: Archaeopteryx's time: just before the end of the Jurassic (Tithonian; 144-150 mys ago) or just before that (Kimmeridgian; 150-156 mys ago).
IMMEDIATE ANCESTOR OF BIRDS: Unknown small arboreal theropod dinosaur, but presumably like Archaeopteryx without feathers, or perhaps resembling a slightly smaller, more arborial version of Sinosauropteryx/Compsognathus or Ornitholestes. This would to all intents and purposes be a maniraptoran (but not as we know it, Tom) because the hands would be used for climbing and predation.
TIME OF FIRST FEATHER: Archaeopteryx's time just before the end of the Jurassic (Tithonian; 144-150 mys ago) or just before (Kimmeridgian; 150-156 mys ago).
EXTINCT FEATHERED GROUPS: All those descended from Archaeopteryx but none other. (Non-feathered dinos to have Archosaur "fur" like Sinosauropteryx's, though evolved separately from mammals'.)
WEAKNESSES: New theory; not supported by faulty cladistics, nor recognised by media. No appealing immediate ancestor of Archaeopteryx offered.
STRENGTHS: Powerfully explanatory:- Explains evolution of feathers as flight enabling feature, and also ownership of feathers by flightless types; explains sudden explosion (not yet fully evidenced, but progressively hinted at) of birds, and particularly larger maniraptorans. Explains other flight-oriented features of larger maniraptorans and their absence pre-A. Provides possible explanantion of disappearance of small pterosaurs on arrival of first birds; BCF and BAND have birds arriving back towards (or in) the Triassic but not making any impact. Shrugs off the chick-digit problem. Allosaurus can have I-II-III if it wants, and Archae & the manis can still have II-III-IV.
PREDICTIONS: MULTIPLE intermediate forms between birds and flightless maniraptors. No pre-Archae early Cretaceous maniraptoran types. Types are descended from Archaeopteryx if and only if they have feathers.
GENERAL COMMENTS: More elegant (with regard to feather ownership) and convincing (ascribes multiple causations) than other theories. Also by far the most interesting since if accepted it will strike a powerful blow at cladistics, and it provides the fascinating thought of all those K manis being flightless birds. Associated with "Trees down" theory. Closely associated with BCF theory (originally); 2F(JJ) holds that birds' ancestors had been arboreal a long time, explaining their absences from the fossil record, but couldn't fly properly because they didn't yet have feathers, only bristles, quills etc. The group name of "Pinnants" has been advocated as a temporary concept, ideally to be replaced at a later date by "birds", regaining their original cladistic definition as anything that has feathers. The BCF notion that many dino types originated in the trees lies easily with 2F. The main difference between the theories is the date of the first feather, and 2F's claim of ancestry to the K maniraptorans and probably arctometatarsalians for Archaeopteryx.
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NAME OF THEORY: BCF - "Birds Came First"
ORIGINATORS: George Olshevsky, inspired by PDW.
TIME OF ORIGIN OF BIRDS: Triassic; first birds also the first dinos.
IMMEDIATE ANCESTOR OF BIRDS: Thecodonts
TIME OF FIRST FEATHER: Triassic
EXTINCT FEATHERED GROUPS: Many non-avian dinos.
WEAKNESSES: Doesn't explain disappearance of small pterosaurs, or explosions of early K maniraptorans and (other) birds; nor why some theropods have feathers and others don't. Since 'all dinos are ex-flying', there is now no special reason why some theropods eg velociraptors should have such special flight-oriented features; also no reason why such a big jump in birdiness should have occured just post Archae. Not supported by media or majority of dinofolk. Cannot explain absence of early birds from typical aquatic pterosaur-bearing deposits of the J & T.
STRENGTHS: Since it suggests Archae's ancestors were small and lived in the trees, probably in forests, it effectively offers an explanation for why they haven't been found.
PREDICTIONS: Triassic feathers; "proper" feathers on many/most dino types, not just theropods. Early but identifiable forms of characteristic K maniraptorans pre-Archae.
CHANGES NEEDED FOR CONVERSION TO 2F: First feather at time of Archae; manis specifically descended from Archae. But these are really only details; 2F is happy with most dino lines being descended from arborial forms, at least in their original days back in the Triassic.
EVIDENCE REQUIRED FOR SUCH CHANGES: Evidence such that pattern of feathered-ness amongst various dinos lines becomes apparent.
GENERAL COMMENTS: Whereas 2F is a phylogeny theory associated with the behaviour theory "Trees down", BCF claims no phylogeny component and merely specialises in being the "Trees Down" behaviour theory par excellence.
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NAME OF THEORY: Sankar Chattergee's theory
ORIGINATORS: SC
TIME OF ORIGIN OF BIRDS: Triassic
IMMEDIATE ANCESTOR OF BIRDS: ?
TIME OF FIRST FEATHER: ?
EXTINCT FEATHERED GROUPS: ?
WEAKNESSES: Predicts Triassic origins for a surprisingly large number of K types eg dromeosaurids. Many find such notions alarming, and it may be said this untestability renders the theory unattractive. Not yet accepted by many.
STRENGTHS: Since many forms are surmised as early as the T, the theory is resistant to positive finds. Originator found the enigmatic "Protoavis"
PREDICTIONS: Predicts Triassic origins for a surprisingly large number of K types eg dromeosaurids.
CHANGES NEEDED FOR CONVERSION TO 2F:No simple change would do it.
EVIDENCE REQUIRED FOR SUCH CHANGES: In 100 years time when none of its pre-Archae predictions have come true, evidence might be considered sufficient.
GENERAL COMMENTS:
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NAME OF THEORY: Larry Febo`s , Birds are Pterosaur Offshoots
ORIGINATORS: May have been briefly considered by Seeley inthe 1800`s. "Seeley (1881) and Weidershiem (1883, 1886) proposed a pterosaur-like ancestor for Archaeopteryx." (The Beginnings of Birds (1985) pg 16.) Otherwise, Larry believes he's the only one proposing this at the moment.
TIME OF ORIGIN OF BIRDS: Mid-Triassic (c 230mya).
IMMEDIATE ANCESTOR OF BIRDS: A hypothetical Pterosaur-bird with small cranium, and relatively small wings, itself descended from the Prolacertiform group (with Cosesaurus as an appropriate example).
TIME OF FIRST FEATHER: Mid-Triassic
EXTINCT FEATHERED GROUPS: Protoavis (of the Triassic),...and of course the late Jurassic and early Cretaceous finds.
WEAKNESSES: Dependant on a hypothetical "missing link".
STRENGTHS: Resolves the "Digit Homology" controversy between the ornithologists and the paleontologists. The missing anterior digit is accounted for as being the pteroid bone, yeilding the homologous digit count 1,2,3 as preferred by paleontologists. Uses minimal dependence on the concept of Convergence.
PREDICTIONS: More pre-Archaeopteryx feathered birds will be found, eventually closing the gap back to the Mid-Triassic.
CHANGES NEEDED FOR CONVERSION TO 2F: Nothing simple would do it.
EVIDENCE REQUIRED FOR SUCH CHANGES:
GENERAL COMMENTS:
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