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Clarifying Terminology ... A Personal Crusade, if You Will
I previous wrote on clarifying terminology and used the example of
"Troodontidae" ... let me use another, and add some examples of
Another example, and one not previously mentioned because the context is
not considered valid, is Thulborn's 1974 phylogeny of ornithischians:
There, he (Thulborn) described both a taxonomy, and a functional
application of terminology to types of pes, and the variation of cursorial
function in ornithischians.
Brachypoda may be a name for a clade, but Thulborn also provided a
functional terminology to the anatomy: brachypodous, femur is longer than
the tibia, metatarsus is less than half the length of the femur, animal is
generally graviportal [= mediportal in the current interpretation, they
could still acheive a fixed-flexed knee and ankle angle during stride
compression phases]; dolichopodous, on the other hand, have a femur
shorter than the tibia, and the metatarsus is longer than half of the
femoral length, generally cursorial. Thulborn also used _dolichopod_ and
_brachypod_ as vernacular taxonomic indicators.
Why do I bring this up? Two reasons: 1) no one seems to operate on this,
and refers to elongate metatarsus and shortened metatarsus ... so much
easier to say dolichopodous or brachypodous in some examples; as 2)
terminology when developed usually has a function, and should be employed
to simplify communication. Recent papers on ankylosaur armor include
several new terms for types of armor, and positions for them:
Tracy L. Ford. 2000. A review of ankylosaur osteoderms from New Mexico
and a preliminary review of ankylosaur armor. _New Mexico Museum of
Natural History and Science Bulletin_ 17: 157-176.
Descriptive placement for armor includes counting the rows from the
midline: "medial" for the sagittal most row, including the first pair of
cervical rings and counted caudally; "primary" for the second row;
"secondary" for the third row; "tertiary" for the fourth row, and also for
the lateral row of pelvic armor, and all other further rows; and "ventral"
for the ... well ... ventral armor. "Cranial" is self-explanatory, and
includes the cheek and nuchal armor, though the gular armor is "ventral;"
"cervical" for the first two cervical rings, fused or not; "pectoral" for
the lateral suprascapular armor and the third cervical ring, which Tracy
identifies as correctly a "pectoral ring" and this includes the shoulder
spikes and the third ring in *Sauropelta*; "thoracic" for the lateral
armor that is not lateral to the pelvis, and the shallow armor for the
back; "pelvic" for the pelvic shield and lateral armor; "caudal" for all
caudal armor and the tail club. The first row (dorsalmost) of caudal armor
is considered "medial," and so forth.
Types of scute description includes terminology for shape:
"square/rectangular/oval/oblong" describe superficial shape. The oval and
oblong descriptors indicate relative mediolateral:craniocaudal lengths,
where oblong is longer than wide compared to oval. "Capped" for scutes
which are rounded, and the apex of the spine does not extend caudally
beyond the basal edge of the element, and is rounded on the dorsal margin;
"pup-tent" for those which are triangular in caudal view, and are inclined
so that the caudal point overhangs the basal edge of the element. "Ridged"
for the gently angled or sloped lateral margins of the median "ridge", and
"keeled" for those in which the edges of the "keel" are vertical or much
more angular to the base. The plates of the cheek are "buccal scutes."
Tracy also applies this terminology in his armor-only diagnoses of
ankylosaurs, and I will get to that in a different post.
William T. Blows. 2001. Dermal armor of the polacanthine dinosaurs. pg.
363-385 in Carpenter (ed.) _The Armored Dinosaurs_ [Indiana University
Blows continues his researches into thyreophore armor with the applied
terminology to types and arrangements of armor, providing more Latinized
terms and vernacular for them. He also attempts to clarify use of "scute"
and "spike" and so forth. Tracy's use of these terms was in reference to
Blows' 2000 paper, so they are not detailed above, but here. For the most
part, descriptions are Blows' _verbatim_, and all essential descriptive
phrases are his.
Ossicle: a dermal element, often round, oval, or subtriangular; larger
ones have peaks or ridges, and have slightly convex or solid flat bases;
found between larger dermal armor, loose, and set in a mosaic.
Plate: a dermal element comprising a tall dorsal keel with rounded or
sharp points. Base is long and narrow and bears rough areas for dermal
Cervical ring: curved group of two to six elements (Tracy counts up to
eight) that surround the dorsal and lateral portions of the cervical
region. Also, Blows does not differentiate the pectoral armor from the
cervical rings, and the third cervical ring of *Sauropelta* is a cervical
ring. Elements may be mounted on a single band or separate bases for each
Scute: a dermal element comprising a low ridges, keeled element of oval
shape, with the keel on the longest axis, which may be displaced laterally
or over the posterior margin of the base. Tracy distinguishes types of
scute as capped or pup-tent shaped. Scutes are incorporated as the
cervical rings, though in some taxa, like *Sauropelta*, another term
Shield: a broad, flat layer of bone covering the pelvic and sacrum,
including presacral rod (= synsacrum), varying in thickness, and built
from a mosaic of bosses and tubercles (see below).
Spine or spike: a dermal element comprising a tall pointed element with
a solid, rounded base, whose diameter is less than the total height. Base
is often offset relative to the spine. The tall dorsal peak is round or
oval in cross section.
Tubercle: raised knobs of bone that are clustered and packed between the
bosses of polacanthine sacral shields. One could use the description to
indicate ventral and gular armor in some taxa, though in others (*Minmi*
and *Dracopelta*) the armor is more plate-like, and a different term is
required (pers. obs.) for these types of armor.
Blows also introduced fancy Latin for some types of scutes and plates:
Capetegulum [pl. capetegulae] ( > caput (Lat.) head + tegula (Lat) tile
= skull tile): the flat bones that cover the skull roof and sides in
ankylosaurian dinosaurs. The buccal, dentary, and even premaxillary and
nuchal armor are examples.
Caudorbitos [pl. caudorbitosa] ( > cauda (Lat.) tail + orbis (Lat.)
circle + os (Lat.) bone = tail-circling bone): the dermal bones that form
the tail club, which in Tracy's terminology would be a pair of successive
medial scutes, and perhaps some neomorphic bone between them in various
Coronux [pl. coronuces] ( > corona (Lat.) crown): these are the caudal
horns of the skull, the squamosal, postorbital, jugal, and quadratojugal
horns of various taxa. These are usually cone-shaped, and those that are
in the upper cranium (postorbital and squamosal) are dorsal coronuces,
those lower (jugal and quadratojugal) are ventral coronuces.
Splate: ( from George Olshevsky's suggestion, > spine + plate
juxtaposed): plate with a spine like anterior leading edge that bears a
point taller than the upper margin of the plate and that tends to incline
posteriorly. Distribution may clear up description, if confusing ... the
caudal armor of *Kentrosaurus*, dorsal plates of *Polacanthus* and
*Hoplitosaurus*, and possibly the parascapular armor of some stegosaurs.
Tricorn ( > tri- (Lat.) three + cornu (Lat.) horn = three-horn): for the
three clustered spikes just caudal to the skull of *Scelidosaurus*, and
possibly for a single spike remnant found applied to *Mymoorapelta* whose
morphology is identical to that in *Scelidosaurus*.
Blows makes further observations on the distribution of dermal armor and
provides a diagnosis for the Polacanthidae based on armor that suggests
the exclusion of *Hylaeosaurus* as well as *Pawpawsaurus*, which had been
considered by some to be polacanthing in relation. It should be observable
from reference to "polacanthines" and similar cited taxa that in _The
Armored Dinosaurs_ there is a prevalent reference of polacanthines to
nodosaurids, rather than ankylosaurids.
Jaime A. Headden
Little steps are often the hardest to take. We are too used to making leaps
in the face of adversity, that a simple skip is so hard to do. We should all
learn to walk soft, walk small, see the world around us rather than zoom by it.
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