ing some observations from evolutionary paleontologists. Chiappe and Bell (2001, p. 556) state: Surprisingly, these [histological] data point at significant differences with respect to living birds. Modern birds usually hatch and develop full-grown sizes within a year. Yet, studies of early birds spread across the evolutionary tree (Archaeopteryx, Confuciusornis, Enantiornithes and others) reveal that these animals had a protracted period of skeletal growth, in which growth was punctuated by annual pauses (phases when skeletal growth slowed down significantly or virtually stopped). Padian (2023, p. 252) concurs: Birds seem to have inherited both high metabolic rates and high growth rates from their dinosaurian ancestors, but by the time the living groups of birds appeared, they had evolved the even-higher rates of growth and metabolism that are observed today10. The first birds took several years of development to reach skeletal maturity11, but today’s birds can do so within a year or less.[emphases mine, footnotes in original] Erickson et al. (2009) note that the “first” birds took longer to mature than most comparably-sized extant birds and that Archaeopteryx took longer to mature compared to extant precocial and alticial land birds. If pre-Flood birds took longer to mature than extant birds, this could be evidence they were living longer than birds of today. However, this pattern may not have held for all ancient birds. According to Feduccia (2006), the bone histology of Cretaceous ornithurines (‘ancient’ birds similar to ‘modern’ birds) is similar to that of modern birds, without growth rings. This could suggest shorter growth intervals, lacking in such pauses. However, Foth et al. (2021) note that juvenile avian fossils are rare, and that most paleo-ontogenetic information from birds comes from Enantiornithes, which took longer to reach skeletal maturity than extant birds. O’Connor et al. (2014) note that “growth in Early Cretaceous birds remains poorly understood.” 4. Slow-growing crocodylians Erickson and Brochu (1999) counted growth rings in the dorsal osteoderms of multiple species of fossil crocodylians and used these data to construct estimated age-versus-length growth curves (Figure 10). The growth curves for the two unidentified species of Deinosuchus from Texas and Montana suggest that these representatives of the ‘terror crocodile’ were particularly slow-growing. If the von Bertalanffy age-versus-length curve from Eq. (14) is a universal one, then it seems Deinosuchus would have still been an adolescent at 40 or 50 years of age. Moreover, because the two Deinosuchus growth curves have not yet ‘plateaued’ or ‘leveled-off’, it seems that the maximum sizes of these two particular species (or perhaps single species) of Deinosuchus could easily have exceeded nine meters. But whatever their final size, their adult forms clearly would have been much larger than adult sizes of extant crocodylians (Figure 10). Likewise, they took much more time to reach maturity than extant forms. Both observations are suggestive of great longevity. The other six crocodylian species apparently did not attain ages or sizes as great as those of Deinosuchus. Smaller adult size could be an adaptation to different environments in the pre-Flood world. However, it could also be an illusion caused by sampling bias: Could these growth curves have been constructed from fossil assemblages of juvenile crocodylians that were separated from larger adults during the Flood? The Leidyosuchus, Pristichampsus, and Brachychampsa growth curves “track” fairly well (Figure 10) with that of the extant American alligator (Alligator mississippiensis), at least for ages less than 25 years. Thus, these particular crocodylians may or may not have taken longer to mature. However, the relatively steep slopes of the “Crocodylus” affinis and Borealosuchus growth curves might imply that these creatures were still ‘adolescents’ at 20-25 years of age. The giant Sarcosuchus imperator also apparently grew quite slowly. Although I have yet to find growth curve data for this species, Sereno et al. (2001) concluded that S. imperator took 50 or 60 years to reach its maximum adult size. Interestingly, Sereno et al. stated in their ab-stract that it had a life-span of 50-60 years. However, this statement is not necessarily correct. Yes, S. imperator apparently took 50 or 60 years to reach maturity, but it is obvious that time to maturity is not necessarily equal to life-span. The osteoderm data give us clues about S. imperator’s time of growth, but they do not tell us anything about how long it lived, as least not directly. But its long maturation period and large adult size (estimated weight of 8 metric tons and length of 11 to 12 meters) could both be indicators of greater longevity compared to extant crocodylian forms. 5. “Old” adolescent sharks Two fossil shark vertebrae suggest that pre-Flood sharks took much longer to grow than extant sharks. By counting presumed annual growth rings in the fossilized vertebrae of a Ptychodus shark from Cretaceous strata in Spain, Jambura and Kriwet (2020) inferred that this Ptychodus shark was 30 years old at time of death. The inferred growth curve indicated that this shark had not yet reached maturity despite its “old” age. Jambura was quoted as saying (Anonymous, 2020): We calculated a size of 4-7 meters and an age of 30 years for the examined shark. It’s astonishing that this shark was not yet mature when it died despite its rather old age . . . . [T]his shark doesn’t show any signs of flattenings or inflections in the growth profile, meaning that it was not mature – a teenager, if you want. This suggests that these sharks grew even larger and older. It’s even more amazing when one realizes that data from a more complete Ptychodus shark fossil (Shimada et al. 2010) suggests that full-grown adults could be 10 to 11 meters long! Shimada et al. (2021) counted growth rings in a Miocene megalodon vertebrae from Belgium. Their constructed von Bertalanffy growth curve (Figure 11) implies that Otodus megalodon would take 498 years to reach 95% of its full adult body length of almost 32 meters. Admittedly, these time and length estimates are probably too high (see downward-pointing arrow in Figure 11), as they imply anterior teeth crown heights more than twice the height of any such megalodon fossil tooth yet discovered. But even if one completely ignores this extrapolation, this particular megalodon was already larger than an extant great white shark at 46 years of age, yet it was apparently HEBERT Allometric and metabolic scaling 2023 ICC 217
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