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Phorusrhacos “wrinkle bearer (jaw)”: Etymology and Meaning

From: Ben Creisler

Since Phorusrhacos Ameghino, 1887 is an icon among prehistoric
animals, and a Cenozoic predatory theropod that retains a certain
dinosaurian allure, I thought it might be good to straighten out the
source and meaning of the oddly spelled name.  Wikipedia has the
etymology wrong as does a 2006 Tetrapod Zoology blog article and
nearly all other sources I am aware of. Apologies for the length here.

Some members of the DML have blogs or write books for popular readers
so the name Phorusrhacos comes up from time to time.

There is also a major conference in Buenos Aires this week about the
history of Argentine paleontology, including a number of dinosaur
items. Addressing a famous Argentine fossil discovery seemed


As an additional connection to dinosaurs, I would cite this bizarre
1895 French illustration of Brontornis and “Phororhacos” living
alongside hadrosaurians:


The article in La Nature theorized that the giant birds may have
coexisted with the last of the dinosaurs in South America during the
Cretaceous and actively preyed on them, likely contributing to their

The French article later appeared in English translation in Scientific
American  (1896):




Ameghino himself never gave the etymology for either Phorusrhacos or
Phororhacos, but there are good clues to what he had in mind. On this
point, I want to acknowledge the late vertebrate paleontologist Donald
Baird, who was interested in nomenclatural history and who steered me
to the correct meaning for Phorusrhacos many years ago.

The name Phorusrhacos (as well as Phororhacos) means “wrinkle bearer
(jaw),” after the rugose (wrinkled) external surface of an incomplete
lower jaw (mandible) that Florentino Ameghino thought belonged to a
toothless edentate mammal at the time he chose the name.

The Neo-Latin element “phorus” (and phoro- in Phororhacos) is derived
from Greek –phoros “bearer, bearing,” a combining form of the Greek
verb phero “bear, carry.”

The element rhacos is from the Greek noun rhakos, meaning “rag,”
“tattered clothing,” “strip of cloth,” but ALSO “wrinkles” and “scars”
or “rents” on the face. See the Ancient Greek meanings at:


For good measure, here’s a link to a Greek-Latin-Spanish dictionary
from the 19th century. Note  the words ruga in Latin and arruga in
Spanish “wrinkle” among the meanings for rhakos.


Phorusrhacos thus might be understood in Spanish as something like
“(mandíbula) que lleva arrugas”

The ONLY source that I found online that had the meaning correct was a
series of trading cards that came out in Britain in 1972. The meaning
for the name Phororhacos was given as “bearing wrinkles”—Alan Charig
apparently wrote the texts for the cards so he may be the source of
the etymology.  I don’t have access to Charig’s 1973 book Before the
Ark to check if he gave an etymology for Phororhacos, as it was then

[NOTE: The spelling Phorusrachos appears to be a reversed version of
the generic name Rhacophorus Kuhl & van Hasselt, 1822 for the flying
frog. Rhacophorus means “rag bearer” [Lappendrager in the original
description in Dutch] for the enlarged pads of skin and webbing on the
front and back feet, but this clearly was NOT the intended meaning for
Ameghino’s name Phorusrhacos.Perhaps Ameghino had originally planned
to use the name Rhacophorus as “wrinkle bearer” but discovered that
the normal-order spelling was preoccupied. Ameghino used a normal
construction for names such as Comaphorus Ameghino, 1886 “hair


The Argentine fossil hunter Carlos Ameghino discovered an unusual jaw
in southern Patagonia in early 1887 and sent it with other new fossils
to his older brother, the noted paleontologist Florentino Ameghino,
then at the La Plata Museum. F. Ameghino published a short description
later in 1887 and initially identified  the fossil as the lower jaw of
an toothless edentate mammal that he named Phorusrhacos longissimus
(“very long wrinkle-bearer (jaw)”).

Ameghino, Florentino (1887): Enumeración sistemática de las espécies
de mamíferos fósiles coleccionados por Carlos Ameghino en los terrenos
Eocenos de la Patagonia austral y depositados en el Museo de La Plata.
Boletin del Museo de La Plata 1: 1-26.


He noted in particular the “ rugosa” [rugose] outer surface of the jaw
bone from openings and indentations for blood vessels. Such a rugged
bone surface would be highly distinctive in a mammal,  thus Ameghino’s
evident grounds for choosing the name “wrinkle bearer.” No other
fossil remains for the taxon were known at the time.


109. Phorusrhacos longissimus, gén. y sp. n. Talla considerable,
comparable a la de un gran Mylodon. Ramas mandibulares inferiores,
bajas, muy largas y completamente desdentadas. Ambas ramas
mandibulares completamente soldadas, formando una sínfisis larga en
forma de pico, convexa abajo, cóncava arriba, rugosa y con numerosos
agujeros vasculares. Alto de la rama horizontal, 56 mm. Longitud de la
parte sinfisaria: por lo menos 15 ctm. (el ejemplar existente está
roto en su parte anterior).

[…Substantial size, comparable to that of a large Mylodon. Inferior
rami, low, very long and completely toothless. Both rami fully fused,
forming a long symphysis in the form of a beak, convex below, concave
above, rugose and with numerous vascular foramina. Height of the
horizontal ramus, 56 mm. Length of the symphysal portion: at least 15
cm. (the existing specimen is broken in its anterior portion).]


In 1889, Ameghino published a more detailed description and emended
the generic name to Phororhacos. He still thought it was a mammal, but
noted that the jaw in life must have had a horny sheath like the beak
of a bird or a turtle.

Ameghino, Florentino (1889): Contribución al conocimiento de los
mamíferos fósiles de la República Argentina. Actas Academia Nacional
Ciencias de Córdoba 6: 1-1028.


The description of the symphysis includes this passage:

…rugosa en toda su extension con un considerable número de agujeros
vasculares de diferentes diámetros, que reemplazan el agujero
mentoniano, acompañados de una considerable cantidad de surcos y
canales vasculares…

[…rugose over its entire extent, with a considerable number of
vascular foramina of different diameters, which take the place of the
mental foramen, accompanied by a considerable quantity of vascular
furrows and channels….]

[NOTE: Many sources state that Ameghino changed the name to
Phororhacos when he realized it was a bird—this is NOT correct as the
1889 paper shows. The emended spelling Phororhacos forms the name in a
more regular way than Phorusrhacos, which has a Latin ending –us oddly
placed in the middle. The names Phorusrhacos and Phororachos have the
same basic derivation and meaning.]


He finally identified the fossil as a giant bird in 1891-- after rival
Argentine paleontologist Francisco Moreno had described Mesembriornis
Moreno, 1889, “southern bird” and after his brother Carlos had written
to him in 1890 to suggest that Phorusrhacos was a bird rather than a
mammal. He blamed his initial error on the unprecedented size of the
jaw for a bird. For the 1891 paper and his drawing of the jaw clearly
indicating the rugose surface, see:


[NOTE: Ameghino sold most of his collection of bird fossils to the
British Museum of Natural History in 1896 for 350 pounds, a decision
he regretted after he became the director of the Museo Argentino de
Ciencias Naturales "Bernardino Rivadavia" in Buenos Aires in 1902. The
original specimen mandible for Phorusrhacos is now BMNH-A530. ]


For an additional brief history:


Blog articles about Ameghino and Phorusrhacos in French (used here for
some historical details):




“rag bearer” –  the right word roots, but inaccurate in the meaning
“rag” for Greek rhakos instead of “wrinkle,” which is the logical
meaning  from Ameghino’s original descriptions as explained above.



“rag thief”—supposedly from Greek phor “thief” and rhakos “rag”.

This false etymology appeared in the Century Dictionary, and is cited
and used in the current English-language Wikipedia article.



“branch” or “branch holder” – in Feduccia 1999 and in Naish 2006

This misreading may be derived from a footnote by P. L. Sclater to an
article by Richard Lydekker in Isis in1893 . Sclater proposed that the
derivation for Phorusrhacos was Greek phoreo [“bear, carry constantly;
wear”] + Greek rhakis “branch” -- and thought the spelling should be
emended to “Phororhacis.” See: