Extinct family of turtles
Protostegidae
is a family of
extinct
marine turtles
that lived during the
Cretaceous
period. The family includes some of the largest sea turtles that ever existed. The largest,
Archelon
, had a head one metre (39 in) long. Like most sea turtles, they had flattened bodies and
flippers
for front appendages; protostegids had minimal
shells
like
leatherback turtles
of modern times.
Anatomy
[
edit
]
As some of the first
marine turtles
, the protostegids set the general body plan for future species of sea turtles. They had a generally depressed turtle body plan, complete with four limbs, a short tail, and a large head at the end of a relatively short neck. Like other sea turtles, they possessed oar-like front appendages especially evolved for swimming in the open ocean. Similar to the still-
extant
, possibly closely related
Dermochelyidae
, protostegids possessed extremely reduced
carapaces
. Some specimens had skeletal protrusions from their ribs almost wrapping around their bodies in place of a complete shell. Like modern sea turtles, protostegids had sharp beaks. One of the defining characteristics of the members of the family was their almost-disproportionately large heads. Specifically, some specimens of
Archelon
have been found with heads one metre (39 in) long. In addition, the members of the family had somewhat reduced plastrons, as well.
[5]
Ecology
[
edit
]
Trophic ecology
[
edit
]
While all members of the family are
extinct
,
palaeoecological
studies on the members of the family have provided some insight into the ecological roles of the Protostegidae. Analysis of fossil organs of some protostegids has revealed entire stomachs containing fossilized
shellfish
.
[4]
[
irrelevant citation
]
The turtles, in turn, are postulated to have been preyed upon by the major predators of the time. Fossil protostegids have been found with tooth impressions from the large
lamnid
sharks of the time.
[6]
Two specimens of
Protostega gigas
have been discovered to have tooth marks from large
sharks
. In addition, teeth of the extinct shark
Cretoxyrhina mantelli
have been found embedded in at least one
Protostega
skeleton.
[7]
Evolutionary history
[
edit
]
The family's oldest members include an
Early Cretaceous
(
Valanginian
) taxon described on the basis of limb bones and shell remains from the
Rosablanca Formation
of
Colombia
,
[2]
Desmatochelys padillai
, known from the specimens recovered from the Early Cretaceous
Paja Formation
of Colombia
[8]
and
Santanachelys gaffneyi
, known from a specimen excavated from
Brazil
in 1998. The latter species first appeared during the Early Cretaceous. As an early sea turtle,
Santanachelys
had several unspecialized characteristics, such as distinguishable digits in its flipper-like arms. Later relatives' flippers were completely fused together for more efficient swimming.
[4]
As with most large
fauna
of the
era
, the Protostegidae died out during the events of the
Cretaceous?Paleogene extinction event
that led to the extinction of the
dinosaurs
.
[9]
The exact
phylogenetic
position of protostegids among turtles is uncertain. Some phylogenetic studies determine the
leatherback turtles
in the family
Dermochelyidae
to be their closest living relatives, with both these families being
monophyletic
.
[4]
[10]
Conversely, the phylogenetic analyses conducted by Joyce (2007) and Anquetin (2012), which included one protostegid species (
Santanachelys gaffneyi
), recovered the family as only distantly related to leatherback turtles. Joyce (2007) recovered Protostegidae as basal
eucryptodiran
turtles lying outside the
crown group
of
Cryptodira
(the least inclusive clade containing all living cryptodirans) and closely related to
Solnhofia parsonsi
;
[11]
Santanachelys
had a similar phylogenetic position in the analysis conducted by Anquetin (2012), who stressed that future studies should include more protostegids to confirm this phylogenetic placement.
[12]
If confirmed, these results would prove that protostegids weren't close relatives of leatherback turtles (or in fact any living cryptodirans), but instead "represent an independent lineage of marine turtles that originated in the Late Jurassic".
[11]
The analyses conducted by Sterli (2010) and Sterli & de la Fuente (2011) recovered
Santanachelys
(and, presumably, the entirety of Protostegidae) as even more distantly related to living cryptodirans; it was found to be basal turtle lying outside the crown group of turtles (the least inclusive clade containing cryptodirans and
pleurodirans
).
[13]
[14]
A phylogenetic analysis conducted by Cadena and Parham (2015) recovered Protostegidae within the crown group of Cryptodira; specifically the family was recovered as belonging to Chelonioidea and more closely related to the
leatherback sea turtle
than
cheloniids
are.
[8]
Taxonomic history
[
edit
]
In 1888, the Belgian zoologist
George Albert Boulenger
published his classification of the
Testudinata
within the 9th edition of the
Encyclopædia Britannica
. The genus
Protostega
was placed within the family
Sphargidae
under the suborder
Athecae
, and the family Protostegidae was named by
Edward Drinker Cope
in 1873.
[3]
A year or so later, the entire suborder was downgraded by
Karl Alfred von Zittel
into a family within the
Cryptodira
.
[15]
In 1994, Hirayama proposed a three-family subdivision of the
sea turtle superfamily
based on
cladistic
analysis; Protostegidae was given full, formal family status in the system, containing most of the
extinct
genera, including
Archelon
, and a previously undescribed protostegid.
[16]
The unidentified specimen was fully described in 1998, as the species
Santanachelys gaffneyi
. The genus
Santanachelys
was appended to the family after the new species was described. This specimen was later to be analyzed to be the family's oldest member.
[4]
References
[
edit
]
- ^
"Protostegidae"
. The Paleobiology Database
. Retrieved
27 July
2013
.
- ^
a
b
Cadena, E.-A.; Combita-Romero, D. A. (2023). "The onset of large size in Cretaceous marine turtles (Protostegidae) evidenced by new fossil remains from the Valanginian of Colombia".
Zoological Journal of the Linnean Society
.
doi
:
10.1093/zoolinnean/zlad053
.
- ^
a
b
Hayden, Ferdinand Vandeveer (1873).
"Sixth Annual Report of the United States Geological Survey of the Territories, embracing portions of Montana, Idaho, Wyoming, and Utah, being a report of progress of the explorations for the year 1872"
.
U.S. Geological and Geographical Survey of the Territories, Annual Report
. Washington D.C.
doi
:
10.3133/70038930
.
- ^
a
b
c
d
e
Hirayama, Ren
(16 April 1998). "Oldest known sea turtle".
Nature
.
392
(6677): 705?708.
Bibcode
:
1998Natur.392..705H
.
doi
:
10.1038/33669
.
S2CID
45417065
.
- ^
Lutz, Peter L.
; Musick, John A. (1996).
The Biology of Sea Turtles
. CRC Press. p. 10.
ISBN
978-0-8493-8422-6
.
- ^
Shimada, Kenshu
; M.J. Everhart; G. E. Hooks III (2002). "Ichthyodectid fish and protostegid turtle bitten by the Late Cretaceous lamniform shark,
Cretoxyrhina mantelli
".
Journal of Vertebrate Paleontology
.
22
(3): 106.
- ^
Shimada, Kenshu
; G. E. Hooks III (January 2004).
"Shark-bitten protostegid turtles from the upper Cretaceous Mooreville chalk, Alabama"
.
Journal of Paleontology
.
78
(1): 205?210.
doi
:
10.1666/0022-3360(2004)078<0205:SPTFTU>2.0.CO;2
.
S2CID
129391058
.
- ^
a
b
Edwin A. Cadena and James F. Parham (2015).
"Oldest known marine turtle? A new protostegid from the Lower Cretaceous of Colombia"
.
PaleoBios
.
32
(1): 1?42.
- ^
Zangerl, Rainer
(May 1953). "The vertebrate fauna of the Selma Formation of Alabama, Part III. The turtles of the Family Protostegidae".
Chicago Field Museum Mem
.
3
(3).
- ^
Meylan, Peter A.
; Ren Hirayama (September 2000). "The Paleontology and Phylogenetics of "Sea Turtles"
".
Proceedings of the 19th Annual Symposium on Sea Turtle Conservation and Biology
.
19
: 104. NOAA Technical Memorandum NMFS-SEFSC-443.
- ^
a
b
Walter G. Joyce (2007).
"Phylogenetic relationships of Mesozoic turtles"
(PDF)
.
Bulletin of the Peabody Museum of Natural History
.
48
(1): 3?102.
doi
:
10.3374/0079-032x(2007)48[3:promt]2.0.co;2
.
S2CID
85998318
. Archived from
the original
(PDF)
on 6 June 2013.
- ^
Jeremy Anquetin (2012).
"Reassessment of the phylogenetic interrelationships of basal turtles (Testudinata)"
.
Journal of Systematic Palaeontology
.
10
(1): 3?45.
doi
:
10.1080/14772019.2011.558928
.
S2CID
85295987
.
- ^
Juliana Sterli (2010).
"Phylogenetic relationships among extinct and extant turtles: the position of Pleurodira and the effects of the fossils on rooting crown-group turtles"
.
Contributions to Zoology
.
79
(3): 93?106.
doi
:
10.1163/18759866-07903002
.
hdl
:
11336/84233
.
- ^
Juliana Sterli and Marcelo de la Fuente (2011).
"A new turtle from the La Colonia Formation (Campanian?Maastrichtian), Patagonia, Argentina, with remarks on the evolution of the vertebral column in turtles"
.
Palaeontology
.
54
(1): 63?78.
doi
:
10.1111/j.1475-4983.2010.01002.x
.
- ^
Baur, George
(June 1890).
"On the Classification of the Testudinata"
.
The American Naturalist
.
24
(282): 530?536.
doi
:
10.1086/275138
.
JSTOR
2450882
.
- ^
Hirayama, Ren
(December 1994). "Phylogenetic systematics of chelonioid sea turtles".
Island Arc
.
3
(4): 270?284.
doi
:
10.1111/j.1440-1738.1994.tb00116.x
.
Further reading
[
edit
]
- Lutz, Peter L.
; John A. Musick (1996).
The Biology of Sea Turtles
. CRC PRess. pp. 432pp.
ISBN
978-0-8493-8422-6
.
- Kazlev, M. Alan
(15 September 2003).
"Mesozoic Marine Reptiles"
.
Palaeos Mesozoic
. Palaeos. Archived from
the original
on 15 July 2007
. Retrieved
3 September
2007
.
- Case, E. C.
(1897).
"On the osteology and relationships of Protostega"
.
Journal of Morphology
.
14
: 21?60.
doi
:
10.1002/jmor.1050140103
.
hdl
:
2027/mdp.39015082583868
.
S2CID
83886426
.
- Cope, Edward Drinker
(1872). "A description of the genus Protostega".
Proceedings of the Academy of Natural Sciences of Philadelphia
: 422?433.
- Cope, Edward Drinker
(1878).
"Note of fossils obtained by Mr. Russell S. Hill, including bones of
Protostega gigas
"
.
The American Naturalist
.
12
(2): 137?138.
doi
:
10.1086/272052
.
- Hay, O.P. (1895). "On certain portions of the skeleton of
Protostega gigas
".
Field Columbian Museum, Publications, Zoological Series
.
1
: 57?62.
- Hay, O.P. (1898).
"On
Protostega
, the systematic position of
Dermochelys
, and the morphogeny of the chelonian carapace and plastron"
.
The American Naturalist
.
32
(384): 929?948.
doi
:
10.1086/277069
.
S2CID
86769103
.
- Sternberg, C.H. (1905). "
Protostega gigas
and other Cretaceous reptiles and fishes from the Kansas chalk".
Transactions of the Kansas Academy of Science
.
19
: 123?128.
doi
:
10.2307/3624190
.
JSTOR
3624190
.
- Wieland, G. R. (1898).
"The protostegan plastron"
.
American Journal of Science
. 4.
5
(25): 15?20.
Bibcode
:
1898AmJS....5...15W
.
doi
:
10.2475/ajs.s4-5.25.15
.
- Wieland, G. R. (1906).
"The osteology of
Protostega
"
.
Carnegie Museum, Memoirs
.
2
(7): 279?298.
doi
:
10.5962/p.234828
.
S2CID
134854045
.
- Wieland, G. R. (1906).
"Plastron of the
Protosteginae
"
.
Carnegie Museum, Annals
.
4
: 8?14.
doi
:
10.5962/p.328715
.
S2CID
251477965
.
- Wieland, G. R. (1909).
"Revision of the
Protostegidae
"
.
American Journal of Science
. 4.
27
(158): 101?130.
Bibcode
:
1909AmJS...27..101W
.
doi
:
10.2475/ajs.s4-27.158.101
.
- Williston, S. W. (1902).
"On the hind limb of
Protostega
"
.
American Journal of Science
. 4.
13
(76): 276?278.
Bibcode
:
1902AmJS...13..276W
.
doi
:
10.2475/ajs.s4-13.76.276
.