DOI: 10.5061/dryad.8931zcs4t
title: Data and code from: Cross-species applicability of a bone-ageing method in delphinids

description: Radiographic evaluation of flipper ossification is a reliable technique
 for age estimation in bottlenose dolphins (Tursiops truncatus), although
 its applicability to other odontocetes remains untested. Interspecific
 differences in flipper morphology and bone development may limit
 transferability or require adjustments for robust application. This study
 applies the bottlenose dolphin framework to common dolphins (Delphinus
 delphis) to characterise developmental patterns, describe morphological
 differences, and evaluate the interspecific application of this method.
 Radiographs from 137 common dolphins aged 0–31 years were examined, with
 bone maturation scored at 16 anatomical sites on the pectoral flipper.
 Several differences were identified, including bilateral asymmetry between
 left and right flippers and the need to adjust long and delta bone scoring
 systems due to interspecific variation in bone maturation. Despite these
 differences, reproducibility between observers was high, and ossification
 scores correlated strongly with age, underscoring the reliability of the
 method. This study provides the groundwork for a species-specific bone
 ageing model for common dolphins by addressing interspecific variation in
 skeletal maturation. One caveat concerns the subtle expression of
 degenerative changes in this species compared with bottlenose dolphins,
 which may limit age estimation precision in older individuals but is
 unlikely to affect accuracy across most of the lifespan. Thus, our
 findings provide the first evidence that, despite morphological
 differences, the method can be successfully applied to common dolphins.
description: # Data and code from: Cross-species applicability of a bone-ageing method
 in delphinids Dataset DOI:
 [10.5061/dryad.8931zcs4t](https://doi.org/10.5061/dryad.8931zcs4t) ##
 Description of the data and file structure **Files:** *
 **Pectoral_fin_data.xlsx** – raw data including bone maturation scores and
 metadata. * **Flipper_development.Rmd** – R code for main analyses. *
 **Inter-observer_error.R** – R code for reproducibility assessment.
 **Regarding Pectoral_fin_data.xlsx:**  **'Left' and
 'Right'** **Sheet "Left" and "Right"** show
 the bone maturation scores for the left and the right pectoral flipper.
 The values for individual bone locations range from -1 to 8 scored based
 on morphological maturation stages. Total bone scores are defined as the
 sum of discrete morphological maturation stages across all flipper bone.
 **Abbreviations are as follows:**  | Abbreviations  | Explanations | |
 :--------------------- |
 :----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | M2pr | Metacarpal 2, proximal epiphysis | | M3pr | Metacarpal 3, proximal epiphysis | | M4pr | Metacarpal 4, proximal epiphysis | | M5 | Metacarpal 5 | | M2dis | Metacarpal 2, distal epiphysis | | M3dis | Metacarpal 3, distal epiphysis | | M4dis | Metacarpal 4, proximal epiphysis | | D2P1pr | First phalanx of digit 2, proximal epiphysis | | D3P1pr | First phalanx of digit 3, proximal epiphysis | | D4P1 (delta) | Proximal phalanx of digit 4, (delta bone) | | D2P1dis | Proximal phalanx of digit 2, distal epiphysis  | | D3P1dis | Proximal phalanx of digit 3, distal epiphysis | | D2P2average | Average score for the second phalanx of digit 2 (calculated from the individual scores of proximal and distal epiphysis)  | | D3P2average | Average score for the second phalanx of digit 3 (calculated from the individual scores of proximal and distal epiphysis)  | | D2P2max | Maximum score for the second phalanx of digit 2 (calculated from the individual scores of proximal and distal epiphysis)  | | D3P2max | Maximum score for the second phalanx of digit 3 (calculated from the individual scores of proximal and distal epiphysis)  | | D2P2min | Minimum score for the second phalanx of digit 2 (calculated from the individual scores of proximal and distal epiphysis)  | | D3P2min | Minimum score for the second phalanx of digit 3 (calculated from the individual scores of proximal and distal epiphysis)  | | Total\_score\_detailed | The total bone score was calculated using all individual bone scores, with the proximal and distal epiphyses of the second phalanges of digits 2 and 3 treated as separate scores. | | Total\_score\_average | The total bone score was calculated using all individual bone scores, with the proximal and distal epiphyses of the second phalanges of digits 2 and 3 represented by their average score. | | Total\_score\_max | The total bone score was calculated using all individual bone scores, with the proximal and distal epiphyses of the second phalanges of digits 2 and 3 represented by their maximum score. | | Total\_score\_min | The total bone score was calculated using all individual bone scores, with the proximal and distal epiphyses of the second phalanges of digits 2 and 3 represented by their minimum score. | **'Proximal-distal development'** Ossification typically begins in the radius, followed by the ulna and then progresses distally into the metacarpals and phalanges. The sheet **'Proximal-distal development'** lists individuals which showed abnormalities with regard to the typical proximal-distal progression of bone maturation.  **'Spearman'** The sheet comprises pooled raw data from the left and right pectoral flippers used to calculate Spearman correlations between bone maturation and age. **'Bilaterality'** The sheet presents total bone scores for the left and right pectoral flippers and compares them to assess whether bilateral differences in bone maturation occurred. **'Delta bone anomalies'** Delta bone maturation typically follows a unidirectional sequence; whereby distal mineralization is not expected until proximal consolidation is complete. In a subset of common dolphins, however, distal ossification frequently began before the proximal center had fully consolidated. This sheet lists the affected animal codes and the maturation stages of the affected delta bones. **'Ashley vs me (R)'** This sheet provides bone scores for animals that were scored by two observers. These raw data were used to assess inter-observer error in assigning morphological bone maturation stages. ## Code/ Software Analyses were performed in **R v4.3.2**. * **Inter-observer error:** potential observer-related bias was tested using generalized linear mixed-effects models (GLMMs; *lme4* package) on a subset of 40 radiographs scored by two independent observers. * **Correlation of ossification scores with age:** relationships between ossification stage and dental age were assessed using Spearman’s rank correlation (ρ), run separately for males and females. * **Precedence matrix analysis:** pairwise comparisons among bones were used to establish the typical developmental order of ossification and to visualize sex- and side-specific variation.