Ecomorfología del cráneo de cinco didélfidos: tendencias, divergencias e implicaciones

Abstract

FORTY-SIX SKULLS OF FIVE SPECIES OF DIDELPHID MARSUPIALS WERE EXAMINED WITH REFERENCE TO THE MASTICATORY AND VISUAL APPARATUSES. THE ANALYSES INCLUDED UNIVARIATE REGRESSION BY REDUCED MAJOR AXES, AND CANONICAL DISCRIMINANT ANALYSIS. CHIRONECTES MINIMUS AND PHILANDER OPOSSUM ARE APPROXIMATELY THE SAME SIZE, BUT THE FORMER SPECIES HAS LARGER TEETH, A WIDE SKULL, AND MORE VOLUMINOUS MASTICATORY MUSCLE MASSES. PROBABLY C. MINIMUS FEEDS ON CRUSTACEANS AND SNAILS, RATHER THAN FISH. P. OPOSSUM AND DIDELPHIS MARSUPIALIS HAVE RELATIVELY SIMILAR SKULLS, WITH ELONGATED MUZZLES AND RELATIVELY SMALL MUSCLES. THIS SUGGESTS A DIET IN WHICH PREDATION ON SMALL VERTEBRATES IS MORE FREQUENT THAN PREVIOUSLY THOUGHT, CALUROMYS DERBIANUS HAS A WIDE SKULL WITH VOLUMINOUS MUSCLES AND SMALL TEETH, SUGGESTING A DIET OF FRUIT AND MANY HARD-SHELLED ARTHOPODS. MARMOSA ROBINSONI HAS THE GREATEST RELATIVE VALUES FOR THE TEMPORALIS, AND LARGE TEETH, BUT AN INTERMEDIATE-SIZED MASSETER. THIS SUGGESTS A DIET BASED ON ARTHROPODS, AND LARGE TEETH, BUT AN INTERMEDIATE-SIZED MASSETER. THIS SUGGESTS A DIET BASED ON ARTHROPODS WITH EXOSKELETONS. THE FIRST CANONICAL VARIABLE ACCOUNTED FOR 83% OF THE INTER-GROUP VARIATION, WHILE THE SECOND CANONICAL VARIABLE ACCOUNTED FOR 11%. HAVING CONTROLLED PARTIALLY THE EFFECT OF SIZE, THE FIRST VARIABLE WAS CORRELATED WITH PROPORTIONAL POSTORBITAL CONSTRICTIION, PROPORTIONAL AREA OF EYE, AND BITE FORCE AT CANINES AND SECOND MOLARS. THERE IS A SUGGESTION OF A TREND TOWARDS CORRELATION BETWEEN RELATIVE EYE SIZE AND PROPORTIONAL LENGTH OF THE TAIL, INSIGUANTING THAT THOSE SPECIES MOVING IN THREE-DIMENSIONAL SPACE NEED LARGER EYES TO ADEQUATELY INTEGRATE THE INFORMATION OF THE ENVIRONMENT.