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Re: Dinosaur Heresies

Larry Smith writes:

>I thought I understood that "brontosaurus" was originally
>reconstructed as a chimera,

Since a) I don't have publicly available archives, b) there's a lot of
people here now that weren't here when Stan Friesen wrote about the
above topic and c) I don't want to make Stan rewrite everything, let
me re-submit something from last year:

--- begin included articles -- MR ---

>From swf@ElSegundoCA.NCR.COM Mon Jun 21 09:43:02 1993
Date: Mon, 25 Jan 93 09:53:51 PST
From: Stan Friesen <swf@ElSegundoCA.NCR.COM>
To: dinosaur@donald.wichitaks.NCR.COM
Subject: Re: Apatosaurus vs. Brontosaurus

O.K.  I now have my notes on the Apatosaurus/Brontosaurus naming

To truly understand what happened, a general understanding of the
official Rules of Zoological Nomenclature is necessary.  This is a set
of rules established by an international group of zoologists to try to
stabilize the naming of animals.

The core principle of the code is that each species has exactly *one*
valid name that is unique to it, composed of two parts: a generic name
and a specific name.  Each generic name must also be unique.

To make this work the code containd many other rules.  For instance,
for a name to even be *considered* as the valid name for a species it
must be properly published in a 'public' manner (that is no mimeo'd
fliers), with a description and differential diagnosis (or a reference
to such), and with a designation of a type specimen. (Or, for a genus,
a designation of a type species).

Now, there are several types of things that can make the prime
directive difficult to attain.  Two (or more) scientists may
independently discover the same form and give it different names, or
two apparently distinct forms may, upon further study, be determined
to be the same.  Or two different researcher may unknowingly give the
same name to two different forms.  Thus there are two more general
principles, the principle of priority - which states that the earliest
publication of a name stands, and later versions are rejected.  The
second is the principle of the first revisor - which states that where
there is ambiguity, or all available names are unusable, the first
correction of the matter is definative.

Now, let us go through the complex history of Apatosaurus.

It starts, strangely enough, with the discovery of a totally different
sauropod.  In 1877 Dr. Lydekker discovered a sauropod he named
Titanosaurus.  (In citation form this is listed as "Titanosaurus,
Lydekker 1887").

Later the same year Nathaniel Marsh discovered a sauropod which he
*also* called Titanosaurus (Titanosaurus, Marsh 1877).  The type
specimen on which this was based was 2.5 sacral centra (a centrum is
the core of a vertebra).  This name, being a junior homonym of
T. Lydekker 1887, had to be replaced.  [The species name was
Titanosaurus montanus].

This he did in a later publication that same year, when he renamed it
"Atlantosaurus montanus".  He also refered a partial skeleton to the
species.  In the same article, Marsh named a new species on the basis
of a partial skeleton and brain case - Apatosaurus ajax. [Note, since
this was later in the paper, Atlantosaurus is considered an earlier
name than Apatosaurus].

In 1878 Marsh gave an isolated femur the name Atlantosaurus immanis.

In 1879 Marsh named a cervical vertebra Apatosaurus laticollis.
Later in the year he described a partial skeleton, lacking a skull,
as Brontosaurus excelsus. [Note, this is the best specimen so far].

In 1881 Marsh found another specimen which he named Brontosaurus

So, at this point we apparently have six species in three genera.

Now, in 1883 Marsh published a large paper in which he made a full
reconstruction of Brontosaurus (probably excelsus).  This
reconstruction was so good that it was widely cited, and the main
plate from this article was widely reproduced.  This was the basis for
the popularity of Brontosaurus.

Now, in 1903 a man named Riggs published a paper in which he proposed
that Apatosaurus and Brontosaurus properly belonged in the same
genus.  Since Brontosaurus was published in 1879 and Apatosaurus in
1877, the rules require that the name of this combined genus be
Apatosaurus.  Over the years Riggs adjustment has come to be
accepted.  Thus the name change is due to Riggs paper, a mere 20 years
after Brontosaurus became popular.

Some later workers have even suggested that Atlantosaurus belongs in
the same genus, but it is generally believed that 2.5 sacral centra
just do not provide a sufficient basis for comparison, so
Atlantosaurus is now mostly considered a 'dubious name', and just left
off by itself.  Even the partial skeleton refered to it in late 1877
has been removed and placed in Apatosaurus excelsus.  But, because
some workers did accept this synonymy temporarily, you may find
Apatosaurus refered to as Atlantosaurus in some publications (since
Atlantosaurus is senior to Apatosaurus in the 1877 paper).

Also, over the years the number of species has been reduced, so there
are now only three 'valid' species, Apatosaurus ajax, Apatosaurus
excelsus, and Atlantosaurus montanus (the last with just one

All of the specimens that Marsh placed in Apatosaurus are now included
in A. ajax, and all of the Brontosaurus specimens are placed in A.

There, does that make everything clear? :-)

sarima@teradata.com                     (formerly tdatirv!sarima)

>From swf@ElSegundoCA.NCR.COM Mon Jun 21 09:58:14 1993
Date: Tue, 25 May 93 08:15:45 PDT
From: Stan Friesen <swf@ElSegundoCA.NCR.COM>
To: dinosaur@donald.wichitaks.NCR.COM
Subject: Re: Dinosaurs on the move in Utah (and elsewhere)

 > Larry Loen writes:
 > >
 > > The Brontosaurus (since it has the old head on it, I'll
 > > call it that) is on a high hill -- very visible.

This is a fairly common misconception, but the name 'change' and the
discovery of the correct head are not related.

The name 'change' is based on the rules of nomenclature, which state
that the oldest name given to an organism is the correct one.  The
name Apatosaurus was applied to a skeleton about 2 years before a
different skeleton was named Brontosaurus.  In the year 1910's another
scientist determined that the two skeletons were from essentially the
same type of animal.  Thus the correct name for both of them is now,
and has been for many years, Apatosaurus.

Because the most popular description of this type of animal had been
published a few years earlier under the name Brontosaurus, and the
joining of the two skeletons was in a scientific journal, the popular
books on dinosaurs did not include this information for many decades
after.  Also, museums are often very slow at changing labels, and all
of the best skeletons had already been put on display under the label
Brontosaurus, so they remained mislabeled until recently.

The correct skull was only discovered about 25 years ago, long after
the name change was established.  But, because this was a spectacular
find, involving an image change, and even a remounting of existing
skeletons, it was picked up quickly by the popular press.  [And of
course, in the course of reporting on this, they also ran across the
correct name, and published that as well].

Now, on the original subject, the Los Angeles Museum of Natural
History has a moderately good collection of dinosaurs on display,
including one of the handful of Tyrannosaurus skulls, and a severely
flattened Triceratops skull, a juvenile Edmontosaurus (perhaps still
labeled under its old name, Anatosaurus), and several others.

sarima@teradata.com                     (formerly tdatirv!sarima)

--- end included articles -- MR ---

Mickey Rowe     (rowe@lepomis.psych.upenn.edu)