Do Bony Orbit Dimensions Predict Diel Activity Pattern in Sciurid Rodents?

Abstract

Diel activity pattern (DAP) is a key aspect of an animal's ecology, but it is difficult to infer when behavior cannot be directly observed, as in the fossil record. Various anatomical correlates have therefore been used to attempt to classify DAP. Eyeball dimensions are good predictors of DAP because they relate directly to light sensitivity of the eye. Osteological characters, such as scleral ring dimensions, are also reliable proxies, but bony orbit dimensions alone have proven less reliable because soft tissues other than the eyeball can affect orbit size and shape. However, it would be useful if bony orbit dimensions could be used to determine DAP, particularly for mammals, which have no scleral ring, and nonmammalian synapsids, which infrequently preserve scleral rings. We investigated the possibility of predicting DAP in sciurids (Mammalia: Rodentia: Sciuridae) using orbit measurements and other cranial dimensions, and a variety of quantitative methods, including phylogenetic flexible discriminant analysis, classification trees, and logistic regression. The latter two methods do not require a priori assignment of DAP and therefore reflect the situation in a fossil data set. We find that although there are some interfering phylogenetic factors, nocturnal and non-nocturnal sciurids can be differentiated from one another with over 80% accuracy using all methods investigated here; attempts to differentiate crepuscular animals from nocturnal and diurnal species proved much less successful. Our results indicate that these analyses offer several viable options for predicting DAP in the fossil record, but such analyses should be conducted in a phylogenetic context whenever possible.

Morphological traits of the eyes of Lepidoptera indicate selection for binocular vision in both diurnal butterflies and nocturnal moths

“…Our finding that nocturnal lepidopterans typically exhibit more ventral-facing eye posi�ons accords with research on rodents, where nocturnal species are more likely to have eyes facing forward in the same direc�on 63,64 . For rodents, the interpreta�on of this characteris�c is that this eye posi�on improves detectability under binocular summa�on.…”

From Fairies to Giants: Untangling the Effect of Body Size, Phylogeny, and Ecology on Vertebral Bone Microstructure of Xenarthran Mammals

“…We determined ecology groups using the primary locomotor ecology of each genus ( Rood 1970 ; Ramsey 1978 ; Navarrette and Ortega 2010 ; Hayssen 2011 ; Hayssen et al 2012 ; Gaudin et al 2018 ; Attias et al 2020 ), and we determined size class based on the groups from GLS regressions ( Table 2 ). Using the same data as the PGLS, we performed the pFDA using code from Motani and Schmitz 2011 and Smith et al 2018 ). This package can only use up to three metrics, so we could not undertake a fully multivariate analysis of our dataset.…”

The oldest semi-aquatic beaver in the world and a new hypothesis for the evolution of locomotion in Castoridae

“…The two target fossils were added a posteriori to determine their likely locomotion. I also used a pFDA to investigate the relationship between astragalar morphology and locomotion [3,[44][45][46]. This is because the long evolutionary history of rodents could have played an important role in shaping their ankle and the sample's distribution across the rodent tree is not random.…”