[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

Re: Brrr, bone chilling paleopolar summers(Polar dinosaur growth and other new papers)



I admit also having trouble understanding Jaime, but this does not
mean it is an error on his part. It may alternatively mean he is
smarter than those among us which have trouble understanding him
(flattering or irony not intended!). This is possible, for at times he
offers observations not shared by the majority which seem to be right
(as for example, the not need to change binomens to make monospecific
or monophyletic genera is one is already of the opinion that genera
are meaningless).

2011/8/9 Jaime Headden <qi_leong@hotmail.com>:
>
> <[F]inding herps is easy via the teeth and scutes any population will leave 
> behind in hard fossil bearing sediments (at J Farlow's Pliocence Pipe Creek 
> site I helped screen in part by heroically hauling lots of sediment full 
> buckets in June the main finding was turtle scutes).>
>
>   I've gotten the impression so far that based solely on Paul's personal 
> experience, he seems to think this should then be true for all geological 
> sites. Isn't this another logical fallacy? Generalizing from the specific, 
> you wish to infer that the absence of a finding means it will be found.

What I understood is that he infers by generalization is that the
absence of a finding (turtle scutes, for example) means it will NOT be
found.

>   Paul should note that, with few exceptions, all Prince Creek sites are 
> monotaxic infills (Fiorillo et al., 2010). Polytaxic assemblages like the 
> Ghost Ranch *Coelophysis* bed have yielded very small numbers of non-theropod 
> taxa, and yet recently, based on deliberative study, new taxa have recently 
> been recorded, including an as-yet unpublished bizarrely prognathic basal 
> theropod.

You refer to Daemonosaurus? If you are, it is already published, even
if not printed 
(http://rspb.royalsocietypublishing.org/content/early/2011/04/05/rspb.2011.0410).

>   similarly, other quarries known and sampled for other a century have 
> yielded the ?silesaurid *Dromomeron roemeri* (Irmis et al., 2007),

Dromomeron is lagerpetid, acording to that article (and others by the
same authors).

>   the Morrison Formation yielded new skeletal remains of the small reptile 
> *Macelognathus vagans* (Göhlich et al., 2005), etc.

Good point. However, these monotypic assemblages may also deliver a
message from which we may also infer different distributions of
dinosaurs and turtles/squamates as supporting inference of different
physiological strategies. First, it would be necessary to introduce
some facts. Turtles, squamates, crocodiles and lissamphibians are not
found nowadays near the northern border of North America and Siberia
(which correspond to tundra biomes), although anurans and squamates
surprisingly reach the northern border of Scandinavia, possibly
because some unique environmental advantage, or because of special
adaptations resulting from stronger selection to tolerate cold
weather, given the difficulty of just retracting southwards with
colder Quaternary epochs because of Scandinavia being limited to the
south by sea. However, a few mammals (48 species according to
Wikipedia) reach the northern borders of these continental masses,
likely because they are physiologically better able to deal with
coldness. It may not look like a statistically significant difference,
if we consider there are about 5000 species of mammals, which
indicates the northern border is also not very hospitable for
homeotherms (most birds migrate in winter, by the way, but for them
migrating is easier).
If we accept that the low diversity on the northern borders are the
result of latitude instead of a given biome as the tundra (unless both
are necessarily associated), then we should expect associations with
low diversity near the northern borders of the northern continents.
Productivity of the tundra may be low because of the predominance of
small mosses and lichens, unable to feed a large diversity of
much-food-needing homeotherms. This would tend to make monospecific
associations more likely than in lower latitudes. Now, if we accept,
as you, that likely ectothermic animal monospecific associations can
be found (as for crocodilians), it may still be significant if we can
found these in lower latitudes, but not in higher ones.

>   Paul is thus saying that the absence of evidence is evidence of absence.

Great point, this relates with the use of negative evidence to
generate hypotheses. Yet, I think we cannot generate distribution or
biogeographical hypotheses without resorting to inference of lack of
taxa. For example, who would say that in the Cretaceous the faunas of
Argentina and Madagascar were more similar than with those in China if
we do not also consider that the clades shared by Argentina and
Madagascar WERE NOT present in China (from which we only have absence
of evidence)?

>   This does not mean that there weren't other types of "herps." But then, 
> since Paul is using a typological term here to refer to a specific 
> paraphyletic group, I am going to assume he is specifically referring to a 
> particular grouping which has not developed any other non-bradymetabolic 
> means of sustaining itself.

True, there are salamanders and fishes wich live in cold streams and
never bask. They simply can be not very active and move function
"cold", even if relatively slowly. Even congelation may not be always
a trouble, because there are frogs which resist congelation.

>   Moreover, you constrain this sentence to "terrestrial ... ectotherms." Good 
> show! Now you can't be wrong, even if a terrestrial croc or lizard were 
> recovered, because it's not a "herp."

More or less: to say they were not ectothermic, it would be required a
specific isotope, histological, or some other kind of evidence, for
parsimony would support these were ectothermic. So in principle,
parsimony may indicate us if the hypothesis is wrong.

>   So at this point, I will take the hint that Paul may be attempting to place 
> the Alaskan chamsposaur there by _accident_,

Point for your position.

>   If the marine reptiles are not endemic to any degree or are not seasonal 
> migrants, then they must be associated; but the same cannot be true for the 
> terrestrial fauna, because it's so much harder to get them a few thousand 
> miles distant. Why then cannot the latter imply the former was migratory? ...

With associated you mean, reaching farther coasts out of the regions
in which they lived moved by something different than its own muscular
power? In such a case, as far as I get your argument, I do not see why
the difficulty of a terrestrial individual to wander on land not
thanks to its muscles beyond the region in which it lives has to
necessarily imply that an individual cannot be thrown beyond the
region in which it lives (being its localization thus better explained
as migration), if we accept the possibilities of distributing
vertebrate individuals by the sea currents are different from those of
the elements in the terrestrial milieu.

>   Paul's argument that reptilian metabolic and thermoregulatory capabilities 
> does not exclude the likelihood of marine ectotherms migrating, and the 
> presence of testudine and champsosaur fossils in the Late Cretaceous 
> sediments of the Colville Basin casts doubt on whether they _could not_.

I know you do not support migration for any terrestrial Alaskan taxon,
but his position on the possibility of terrestrial ectotherms not
migrating is logically defensible if you have some physiological
reason which suggests ectotherms cannot migrate, if we expect that
they had a physiology similar to their recent relatives (which is the
EPB-wise most parsimonious hypothesis unless some new evidence
indicating a different physiology arises). Accepting the presence of
ectotherms near the northern continental border you indicated, I
prefer the possibility that the terrestrial ectotherms were endemic
and tolerated the harsh climate, which you suggested before for the
dinosaurs, instead of being migratory, if only because it seems
cheaper to resist coldness than performing trips to relatively far
regions with significatively different climates.

>  Paul attempts to dismiss this by casting this material as floaters or 
> "wanderers," or accidental corpses. The range of exceptions to migration 
> being brought up, including the ludicrous amount of distance to bring 
> otherwise southern Canadian taxa into the Arctic, stretches credulity.

They may come from other close, not emerged, intermediate lands, thus
narrowing the distance. I think you are right however, if the turtles
and champsosaurs in question are not marine themselves. Rivers
originating farther south may theoretically carry corpses of
freshwater creatures to northern latitudes beyond the climate in which
the living creature thrived less randomly, but the longer the traject
traveled by a corpse through rive, the greater has to be the power of
its waters, which tend to carry large blocks of sediment which would
crush whatever corpse there was there, likely beyond recognition.
Neither do I know of rivers with these features.

Cheers,

Augusto