Largest animal of today versus the largest animal in history
The current heavyweight champion
It is well known that the blue whale is the largest animal ever measured, with a length of 33 meters and the heaviest recorded mass at 199 metric tonnes. The average length of this species is around 21 meters to 30 meters, including variations of the subspecies present. These measurements far surpass almost every other animal that are not blue whales themselves, and the biggest among them yet.
To reach and maintain such enormous mass and size, the whales need access to an inordinate amount calories, which they fulfill by filter feeding; using their mouth to trap vast swaths of seawater, and later pushing it out with their elastic tongues, trapping only krill (small shrimp-like animals that drift in the ocean) with the baleen (bristle like teeth) and swallowing the krill. The high caloric density of krill allows filter feeding to be more efficient than active predation, and by a significant margin. Only in recent years have blue whales and other filter feeders had access to such a rich source of food, as the earth’s climate shifted recently to permit a massive increase in plankton production, which allowed the krill to be ever more plentiful.
Being this large allows the blue whale to not be worried of any predator, with the exception of smaller individuals being hunted down by large orca pods (Orcas hunt in synchronized groups called pods, the size of these pods may reach over 70 individuals). Even with such size, the whales are capable of complex maneuvers when krill hunting, exemplifying its specialist adaptations and intellect.
The size and mass of the blue whale remains unchallenged by all other animals of today.
The largest from a bygone era
In recent years, an ancient creature of leviathan proportions was described by paleontologists, Ichthyotitan Severnensis; the largest marine reptile to ever swim. It is related to the family of ichthyosaurs called shastasauridae, living during the tail end of the triassic, and its most recent member.
Ichthyotitan is believed to have been an active predator, being the apex of the triassic seas. This is what makes it different from other large animals, it is not a filter feeder, while that makes it harder for animals to grow past certain sizes, it being the absolute apex made nothing off the menu for it. While primary production needs to be extremely high to sustain such a calorically intensive species, it is known that ecosystems have been able to support multiple large apex predators in the past; i.e., the western interior seaway supporting Mosasaurs, Elasmasaurs, Cretoxyrhina, etc. Each species co-existed at the same time sharing some of the same habitat while being larger than orcas and some reaching sperm whale sizes and mass. Clearly, the mysterious ocean can house such wonders, regardless of if we understand how exactly; the ocean is very secretive.
Ichthyotitan is currently described from two specimens, each containing only a fragmentary surangular bone (base of the lower jaw), measuring to be just over a meter long, with the estimated complete bone being over 2 meters.
(Picture of the surangular; most complete parts)
Now, this is really, really, really little to go off by to claim a species was the largest ever… at first glance. The surangular bone is unique in many of its characteristics, with it being the base of the jaw, it is hard to be mistaken for other bones with high level analysis. The scaling of the jaw and head is very definitive with the surangular, and the surangular scales very reliably with itself. Although Shastasaurus have a bit of variance with the ratio of head to body length, even the smaller estimates land the Ichthyotitan at 20 meter length, while the most reasonable estimates give it a length of 26 meters. Keep in mind, the fragments found were of developing specimens, so the maximum length may very well be over 30 meters or further.
These are just the published and official estimates, after the description of the second surangular, which was mistaken for a dinosaur femur, paleontologists have had a renewed interest in going over the odd fossils that resembled the surangular but were never described in depth. Specialist Dean Lomax (who described Ichthyotitan and the current leading Ichthyosaur researcher) said that a few more suspected Ichthyotitan specimens have been found, which has increased the estimated length of the beast, but the research is not complete on that yet. If you want reliable Ichthyosaur research, always bet on Lomax.
Undeniably, this species reached great sizes, rivaling the biggest alive today. Discovery of this titan shows how little our understanding of life is and how it blooms in nature, effortlessly. Even still, Ichthyotitan is the only rival for the blue whale in terms of volume, the crown for the heaviest animal ever goes to another monster from a forgotten time…
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