1999 Number 1
8 June 1999
CONTRIBUTION TO THE SYSTEMATICS OF CAIMAN LATIROSTRIS (DAUDIN, 1802) (CROCODYLIA, ALLIGATORIDAE)
M. Crea, J. Merler, and R. Quintana.
1989. Anales del Museo de Historia Natural de Valparaíso 20: 75-80.
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Contemporary Herpetology
Information Series 1999 Number 1 8 June 1999 |
ISSN 1097-7112 |
CONTRIBUTION TO THE SYSTEMATICS OF CAIMAN LATIROSTRIS (DAUDIN, 1802) (CROCODYLIA, ALLIGATORIDAE)M. Crea, J. Merler, and R. Quintana. |
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Translated by Brian R. Warren (bwarren@selu.edu)
Department of Biological Sciences
Southeastern Louisiana University
Hammond, Louisiana 70402 USA
INTRODUCTION TO ENGLISH VERSION
While reviewing the pertinent literature for a planned project on caiman systematics, I came across this Crea et al. paper, which refutes Freiberg and Carvalho's (1965) proposed subspecies of the broad-snouted caiman, Caiman latirostris. Both of these papers were originally published in Spanish-language journals, and I took the liberty of translating the Crea et al. paper for use in my research. Recognition of subspecies, as a general notion, is a practice that has done systematics much more harm than good, and the subspecies debates pertaining to crocodilians have been particularly odious. Frair and Behler (1983. Review of Liste der Rezenten Amphibien und Reptilien. Testudines, Crocodylia, Rhynchocephalia. Herpetological Review 14: 23-25) illustrate some of the problems created when subspecies of common caimans and Nile crocodiles are described using commercially-processed skins with no type localities. Fortunately, Freiberg and Carvalho cannot be accused of this sort of error. Instead, Crea et al. show that they simply recognized a non-existent partition of broad-snouted caiman diversity. I would like to express my sincere gratitude to Dr. Sergio O. Zunino of the Museo de Historia Natural de Valparaìso for granting permission to publish the English version of this paper.
B.R.W.
CONTRIBUTION TO THE SYSTEMATICS OF CAIMAN LATIROSTRIS (DAUDIN, 1802) (CROCODYLIA, ALLIGATORIDAE)
M. Crea, J. Merler, and R. Quintana
INTRODUCTION
The order Crocodylia in South America presently consists of the genera Caiman, Melanosuchus, Paleosuchus, and Crocodylus. The alligatorid species, Caiman latirostris, was described by Daudin (1802) as Crocodylus latirostris. This species has been cited as Caiman latirostris (Daudin) Gray 1862, Alligator latirostris (Daudin) Strauch 1866, and Jacare latirostris (Daudin) Gray 1872.
Freiberg and Carvalho (1965) recognized two subspecies that they named Caiman latirostris latirostris and Caiman latirostris chachacoensis [sic]. In keeping with that contribution, subsequent studies of that species have cited both subspecies (Vaz Ferreira and Achaval, 1975, 1980). Nevertheless, Medem (1983), as well as Federico Achaval (pers. comm.) cast doubt on the validity of those subspecies.
The purpose of this work is to determine the taxonomic validity of the proposed subspecies of Freiberg and Carvalho (1965), using a comparative analysis of morphological characters (cranial osteology and scutellation).
MATERIALS AND METHODS
Material examined and criteria for measuring the skulls:
The material studied came from the following collections:
MACN: Museo Argentino de Ciencias Naturales "Bernardino Rivadavia," Buenos Aires.
MACN CABa: MACN "Avelino Barrio," Buenos Aires.
MLP: Museo de Ciencias Naturales, La Plata, Bs. As.
MCNAB: Museo de Ciencias Naturales, "Amado Bompland," Corrientes.
MER: Museo de Ciencias Naturales y Antropologica, Paraná, Entre Ríos.
MPCNFA: Museo Provincial de Ciencias Naturales "Florentino Ameghino," Santa Fe.
Zoo. Bs. As.: Jardín Zoológico de la Ciudad de Buenos Aires.
IUCN: International Union for the Conservation of Nature/Natural Resources.
Col. Pers.: personal collection.
For the skull measurements (Figure 1), we followed the criteria of Iordansky (1973), according to the following details:
Cranial width (AC): between the lateral surfaces of the mandibular condyles of the quadrates.
Dorsal cranial length (LC): from the point of the snout to half of the posterior margin of the skull roof.
Maximum length of the palatine fossas (LFP): length of the palatine fossas in the most extended part, between the pterygoids and the maxilla.
Maximum width of the palatine fossas (AFP): width of the palatine fossas in the most extended part, between the ectopterygoids and the palatine.
Width of pterygoids (AP): width of the portion of the pterygoids that participate in the formation of the palatine fossa.
Suture of pterygoids-ectopterygoids (SPE): straight line or broken line.
Form of palatine fossas (FP): rhomboid or subtriangular.
Index of palatine fossas (IFP): (AFP/LFP)x100.
Cranial relation (RC): Cranial width/cranial length.
Skins:
| Figure 1. Morphological characters of the skull of Caiman latirostris 1. skull width; 2. skull length; 3. palatine fossa length; 4. palatine fossa width; 5. pterygoid width; 6. pterygoid-ectopterygoid suture. |
In measuring the skins, we followed the method adopted by Medem (1981, 1983), counting in each case the number of rows of ventral transverse scales; those that extended from the first row situated directly behind the anterior extremities to the anterior border of the cloaca (Figure 2).
We measured live animals (wild) from: Resistencia, Chaco (3
examples in 1985); estancia San Juan Poriahú , Depto. San Miguel, Corrientes (1 example
in 1986); Zoológico de Roque Saenz Pena, Chaco (7 examples in 1986 coming from the
"La Mora" region of Chaco); and Zoológico de La Plata (2 examples in 1985,
without locality data).
| Figure 2. Ventral view of Caiman latirostris, showing the number of ventral scale rows (NFV). |
RESULTS AND DISCUSSION
To describe their subspecies, Freiberg and Carvalho (1965) presented the following key to distinguish them:
1. Palatine fossa elongate (Index: (width/length) x 100 =
50-58); pterygoids share in the posterior border of the palatine fossa with a wide bridge;
22-24 ventral posterior scale rows; cranial relation (width/length) = 1.4-1.5 … C.
latirostris latirostris (Daudin)
2. Palatine fossa short (Index: (width/length) x 100 = 61.2-66.9); pterygoids share in the
posterior border of the palatine fossa with a narrow bridge; 24-27 ventral posterior scale
rows; cranial relation (width/length) = 1.1-1.3 … C. latirostris chacoensis n.
ssp.
According to those authors, C. l. latirostris has a distribution that includes ". . . from Río Grande do Norte to Río Grande do Sur, by the Atlantic slope of Brazil, by Espírito Santo, Río de Janeiro, Sao Paulo, and Sta. Catharina; Salto and Artigas Departamentos in Uruguay and Alto Paraná, Misiones to 27° 30’ S in Argentina, whereas C. l. latirostris [sic; chacoensis?] inhabits the provinces of Entre Ríos and Santa Fe, to 32° S in Corrientes, Chaco, Formosa, and Jujuy, Argentina."
Nevertheless, in analyzing the available material, we found that certain skins and skulls, some of which also were utilized by Freiberg and Carvalho (op. cit.), have characteristics of both supposed subspecies, like the following:
I. One of the specimens (MER 542) proposed as a paratype of C. l. chacoensis by those authors corresponded, according to the index of the right palatine fossa (63.30), to this subspecies; however, the measurements of the left palatine fossa (index 57.50) corresponded to C. l. latirsostris. This same problem occurred in evaluating example MACN 30612, with a right palatine fossa index within the supposed range of C. l. latirostris (56.10), but with an index of 61.20 for the left fossa, which coincides with C. l. chacoensis. We observed this same situation in MPL S/N, which had a right fossa of 58.3 (C. l. latirostris), but a left of 62.5 (C. l. chacoensis) (Table 1).
II. Upon measuring skulls 7830 and 3110 of the MACN that are figured in Plate 1 of Freiberg and Carvalho (1965), the first of these (proposed as a paratype of C. l. chacoensis) presents a straight-line suture between the pterygoids and ectopterygoids, while the diagnosis of C. l. chacoensis says, ". . . ectopterygoid-pterygoid suture in a broken line."
In the second (proposed as C. l. latirostris), the indices of the right and left palatine fossas are 62.50 and 61.00, respectively, which correspond to the other subspecies and the form of the fossas is clearly rhomboid. That, combined with the shape of the pterygoid-ectopterygoid suture, is indicative of a correspondence to C. l. chacoensis and not to C. l. latirostris as suggested by Freiberg and Carvalho, according to their own arguments (Table 1).
III. With reference to the cranial relation, we find that the examples MACN 30565-30570, 30610; MER 540; Zoo. Bs. As. 1-2 and Col. Pers. 2-3, putatively belonged to C. l. latirostris but according to the other diagnostic characters, they belong to C. l. chacoensis(Table 1).
IV. With respect to scutellation, both subspecies are differentiated according to the key of Freiberg and Carvalho (1965) in this way: C. l. latirostris has between 22-24 ventral scale rows, while C. l. chacoensis has between 24-27 ventral scale rows.
Of 107 examples of C. l. latirostris measured in Brazil by Carvalho (1955), 24 (22.5%) were not able to be classified using the key mentioned previously because they possessed 24 ventral scale rows. The same problem occurred with 3 examples (17.7%) out of a total of 17, measured in Uruguay by Medem (1983); also with 7 examples (70.0%) out of a total of 10, measured in Uruguay by Vaz Ferreira and Achaval (Medem, 1983) and with 10 examples (22.7%) out of a total of 46 measured in Argentina for this study (Table 2 and Table 3).
Table 1.
Cranial Characters Analyzed (measurements in centimeters)
| Collection Number | Cranial width | Dorsal cranial length | Maximum length of the palatine fossa (left) | Maximum length of the palatine fossa (right) | Maximum width of the palatine fossa (left) | Maximum width of the palatine fossa (right) | Pterygoid
point width (left) |
Pterygoid
point width (right) |
Ectopterygoid- pterygoid suture | Form
of palatine fossa |
Index
of palatine fossa (left) |
Index of palatine fossa (right) | Cranial relation | |
| MACN | ||||||||||||||
| 7021 | 14.50 | 20.00 | --- | 4.60 | 2.50 | 2.70 | 0.30 | 0.36 | broken | rhomboid | --- | 58.80 | 1.38 | |
| 7375 | 21.50 | 27.70 | 6.35 | 6.40 | 3.50 | 3.50 | 0.34 | 0.33 | broken | --- | 55.10 | 54.70 | 1.29 | |
| 7830 | 21.00 | 27.00 | 4.10 | 4.00 | 3.20 | 3.30 | 0.10 | 0.40 | straight | rhomboid | 78.00 | 82.50 | 1.28 | |
| 12586 | 23.50 | 28.00 | 5.90 | 5.60 | 3.60 | 3.50 | 0.70 | 0.60 | broken | rhomboid | 61.00 | 62.50 | 1.19 | |
| 15232 | 19.70 | 23.00 | 6.10 | 6.00 | 3.50 | 3.30 | 0.40 | 0.40 | broken | rhomboid | 57.40 | 55.00 | 1.16 | |
| 30565 | 11.50 | 17.80 | 4.20 | 4.30 | 2.10 | 2.20 | 0.32 | 0.34 | broken | rhomboid | 50.00 | 51.20 | 1.55 | |
| 30566 | 11.80 | 17.30 | 4.00 | 4.00 | 2.50 | 2.50 | 0.70 | 0.70 | broken | rhomboid | 62.50 | 62.50 | 1.47 | |
| 30567 | 8.80 | 13.70 | 3.40 | --- | 1.70 | 1.70 | 0.38 | 0.24 | broken | rhomboid | 50.00 | --- | 1.55 | |
| 30568 | 15.50 | 22.00 | 5.00 | 5.10 | 3.10 | 3.10 | 0.30 | 0.40 | broken | rhomboid | 62.00 | 60.80 | 1.42 | |
| 30569 | 6.30 | 9.80 | 2.50 | 2.40 | --- | 1.30 | --- | 0.30 | broken | rhomboid | --- | 54.20 | 1.55 | |
| 30570 | 9.00 | 13.70 | 3.30 | 3.20 | 2.00 | 2.00 | 0.60 | 0.50 | broken | rhomboid | 60.60 | 62.50 | 1.52 | |
| 30572 | 8.50 | --- | 3.80 | 3.60 | 1.70 | 1.60 | 0.42 | 0.36 | broken | rhomboid | 44.70 | 44.40 | --- | |
| 30610 | 12.20 | 18.50 | 4.40 | --- | 2.50 | --- | 0.38 | --- | broken | rhomboid | 56.80 | --- | 1.52 | |
| 30611 | 8.40 | --- | 3.50 | 3.40 | 1.80 | 1.90 | 0.40 | --- | broken | rhomboid | 51.40 | 55.80 | --- | |
| 30612 | 13.30 | 21.00 | 4.90 | 4.90 | 3.00 | 2.75 | 0.50 | 0.50 | broken | rhomboid | 61.20 | 56.10 | 1.58 | |
| MCNAB | ||||||||||||||
| 9 | 21.50 | 28.50 | 6.30 | --- | 3.70 | --- | 0.70 | --- | broken | rhomboid | 58.70 | --- | 1.32 | |
| MPCNFA | ||||||||||||||
| 8 | 6.20 | 9.10 | 2.50 | --- | 1.30 | --- | 0.20 | --- | broken | rhomboid | 52.00 | --- | 1.47 | |
| MER | ||||||||||||||
| 539 | 17.50 | 23.20 | 4.90 | --- | 3.30 | --- | 0.50 | --- | broken | subtriangular | 67.30 | --- | 1.32 | |
| 540 | 13.50 | 19.80 | 4.80 | --- | 2.80 | --- | 0.50 | --- | broken | rhomboid | 58.30 | --- | 1.47 | |
| 541 | 23.50 | 31.50 | 7.00 | --- | 3.80 | --- | 0.50 | --- | straight | rhomboid | 54.30 | --- | 1.34 | |
| 542 | 20.50 | 27.20 | 5.20 | 4.90 | 3.00 | 3.10 | 0.10 | 0.10 | broken | rhomboid | 57.70 | 63.30 | 1.32 | |
| MLP | ||||||||||||||
| S/N | 14.40 | 19.50 | 4.80 | 4.80 | 3.00 | 2.80 | 0.50 | 0.60 | broken | rhomboid | 62.50 | 58.30 | 1.35 | |
| Zoo Bs. As. | ||||||||||||||
| 1 | 12.90 | 19.10 | 4.50 | 4.80 | 2.30 | 2.40 | 0.40 | 0.70 | broken | rhomboid | 51.10 | 50.00 | 1.48 | |
| 2 | 19.80 | 27.80 | 5.60 | 5.20 | 3.20 | 3.00 | 0.50 | 0.40 | broken | rhomboid | 57.10 | 57.70 | 1.40 | |
| Col. Pers. | ||||||||||||||
| 1 | 16.80 | 23.00 | 5.10 | 5.00 | 2.70 | 2.60 | 0.20 | 0.30 | broken | rhomboid | 52.94 | 52.00 | 1.37 | |
| 2 | 12.30 | 18.00 | 4.30 | 4.40 | 2.50 | 2.50 | 0.50 | 0.40 | broken | rhomboid | 58.20 | 56.90 | 1.46 | |
| 3 | 12.10 | 17.20 | 4.40 | 4.50 | 2.45 | 2.55 | 0.50 | 0.45 | broken | rhomboid | 55.68 | 56.66 | 1.42 | |
| 4 | 15.90 | 19.80 | 4.63 | 4.60 | 2.73 | 2.60 | 0.40 | 0.40 | broken | rhomboid | 58.96 | 56.52 | 1.24 | |
|
Source: I = Carvalho 1955; II = Medem 1973; III = Vaz Ferreira and Achaval 1977; IV = this work. |
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In regards to the geographic distribution proposed by Freiberg and Carvalho (1965) for both subspecies, we find contradictions when analyzing the measurements of skins and skulls:
1. In accord with the data obtained by Carvalho (1955), C. l. chacoensis is found also in Brazil, contrary to the distribution proposed by Freiberg and Carvalho (1965). Moreover, a greater number of the caimans he caught in Brazil were examples of C. l. chacoensis (46.7%) than of C. l. latirostris (30.8%) (Table 3).
2. In a similar way, regarding the examples measured by Medem in the museums of Urugay in 1973 and in accord with the key of scutellation characters, 23.5% of these belonged to C. l. chacoensis. Recently, we found another contradiction with the proposed distribution: namely that C. l. chacoensis should not be found in Uruguay. We should take into account that Medem himself (1983) with respect to Uruguay indicated ". . . C. l. latirostris . . . according to its geographic distribution, should belong to this subspecies, but the skulls that we saw with herpetologist F. Achaval, showed anatomical characters as much like C. l. latirostris as like C. l. chacoensis." (Table 3)
In the part dedicated to Argentina, Medem (1983) affirmed that ". . . the only skull that we got from the swamps of Iberá (Corrientes), shows characteristics of both (subspecies). This indicated that very probably the subspecific characters are not fixed, without variables, which casts doubt on the validity of these (subspecies)."
3. Also in the material analyzed by Vaz Ferreira and Achaval (Medem, 1983) in Uruguay, we found 30% of the examples belonged to C. l. chacoensis, repeating the contradiction observed in the above point (Table 3).
4. The ten skulls of the MACN collection (30565-30570, 30572 and 30610-30612) belonged to Caiman latirostris. According to the index of palatine fossas, seven of those corresponded to C. l. latirostris and only 3 to C. l. chacoensis. That is to say, we found individuals of the two subspecies in the same locality, or being in the condition of sympatry.
5. Also we had found examples that by the index of palatine fossas corresponded to C. l. latirostris, but those originated from localities very distant from the proposed borders of this subspecies. We found the following skulls in this condition: MACN 7021, Jujuy; 12532, Manantiales (Corrientes); MCNAB 9, Corrientes; MPCNFA 8, Pto. de Santa Fe; MER 540 and 541, Montecarlo (Misiones); MLP S/N, Corrientes; Zoo Bs. As. 2, Ramón Lista (Formosa); Col. Pers. 1, Santo Tomé (Corrientes); 2, Bella Vista (Corrientes); 3, Loreto (Corrientes); 4, Santa Fe.
CONCLUSIONS
In accordance with our results and those of the works cited, we observe that the characteristics postulated for separating the two subspecies of Caiman latirostris cannot be considered definitive on the basis of the following considerations:
a. With respect to the index of the palatine fossas, there are examples that have indices of both subspecies. Likewise, using this index, there exist examples that do not belong to either subspecies.
b. As regards the pterygoid-ectopterygoid suture, it is described in C. latirostris chacoensis as a broken suture. However, the majority of skulls that were measured had broken sutures, including those examples that, according to the index of palatine fossas, corresponded to C. l. latirostris.
c. The same problem occurred in the shape of the fossa. C. l. chacoensis is described with a rhomboid palatine fossa and C. l. latirostris with a subtriangular fossa. The majority of the examples measured presented a rhomboid palatine fossa, including those examples which, according to the index of palatine fossas, corresponded to C. l. latirostris.
d. As regards the participation of the pterygoids in the palatine fossa, it was necessary to clarify what is meant by a wide or narrow point; also it was crucial to know the range of variability of the subspecies. Besides, we could not correlate the selected variables in the subspecies. Thus, for example, there were skulls that were distinguishable by the different indices of palatine fossas, but that had pterygoid points similar in size. On the contrary, there were others which shared an index value, but differed in the width of the pterygoid point.
e. With respect to scutellation, specifically to the rows of transverse ventral scales, it was necessary to redefine the ranges between which lie the two subspecies, because those which were proposed gave way to confusion. Many examples were encountered that, because they possessed 24 scale rows, could not be assigned to a particular subspecies.
f. With the geographic distribution, contradictions exist. The presence of C. l. chacoensis in Uruguay (Medem 1983), in Brazil (Carvalho 1955), and the fact that many of the Argentinian broad-snouted caimans [used ambiguous vernacular term] belong to C. l. latirostris, casts doubt on the distributions mentioned in the original description of the two subspecies. To these points we add that several times caimans were found from the same locality that belonged to both subspecies.
Finally, in accordance with the above points, we consider that the characteristics proposed by Freiberg and Carvalho cannot be taken as valid for the differentiation of the two subspecies of Caiman latirostris, because they are too variable and there are too many counterexamples. For these reasons, we confirm the validity only of Caiman latirostris (Daudin, 1802).
ACKNOWLEDGEMENTS
The authors acknowledge the official entities and all those
persons who offered their generous and ample cooperation for the realization of this work.
To Drs. José M. Gallardo, Jorge Cranwell, and Raúl H. Aramburu; to Lic. Esteban D.
Astort, Carlos Virasoro, and Federico Achaval; to Tomás Waller and Jorge D. Williams and
to Professor Julio R. Contreras.
We particularly wish to thank Dr. Zulma B. de Gasparini, of the Vertebrate Paleontology
Section of the Museo de La Plata, for her scientific guidance and for the bibliographic
material furnished and also for her constant interest and encouragement.
REFERENCES
Submitted: Mon, 05 Oct 98 13:21 CST
