first entry is actually the oldest animal on the list. Dunkleosteus
was a placoderm
(specifically an arthrodire placoderm) fish that
lived during the Devonian period when vertebrates were only just
starting to live on the land. Placoderms had bony external growths
on their bodies which is why they are often referred to as armoured
fish. In the case of Dunkleosteus this bony
armour was around the
head and neck, and is to date the only parts of this fish that are
known. It would seem however that this ‘armour’ was not so much
for protection but to allow for the fixing of immensely powerful biting
muscles. Additionally the armour formed both the upper and lower jaws
to produce two bony plates that ground against one another, forming
two sharp blades to give Dunkleosteus a shearing
bite. These blades
combined with the powerful jaw closing muscles that provided
Dunkleosteus with one of the most powerful bites in
the fossil record
gave Dunkleosteus the ability to slice through
anything it placed in
its jaws including other armoured placoderms.
Anyone who still doubts the placement of Dunkleosteus onto a list like this needs to remember one thing. The sharks did not reach large sizes or a level of development where they could be described as the dominant predators of the ocean until several million years after arthrodire placoderms like Dunkleosteus went extinct.
on the list, Shastasaurus grew
up to a total of
21 meters long which makes this the largest marine reptile so far
known. However the remains that prove this were originally attributed
to another large ichthyosaur named Shonisaurus,
which is why some out
of date reports still claim Shonisaurus to be the
Aside from possibly being the largest creature on this list, Shastasaurus is probably the most specialised with a preference for squid. Study of the short snouted skull suggests that the jaws could open so wide and so fast that they would create a sudden vacuum inside Shastasaurus’s mouth, sucking in anything that was in front of it. As such Shastasaurus did not have to bother with teeth in its jaws, nor did it have to expend vast amounts of energy pursuing prey. All Shastasaurus had to do was glide to where the squid were and open its mouth.
is often just described as a plesiosaur,
but in fact it is
representative of a group of plesiosaurs that had proportionately
longer necks. Known as the elasmosaurids, some of these grew to not
only become the largest plesiosaurs, but also some of the most
Elasmosaurus had enlarged teeth that intermeshed together when the jaws closed so that anything between the jaws would be speared by them so that the prey could not escape. Associated fossil evidence of some specimens not only shows that marine reptiles like Elasmosaurus had a particular preference for fish, but that they also swallowed stones to act as gastroliths. Early interpretation of these stones was that they provided ballast to counteract the lifting effect of the air in the lungs but two observations cast doubt upon this. One is that when gastroliths are weighed the combined weight is usually only a small fraction of the total weight of the animal. Two, is that fossils of fish bones have been found amongst these gastroliths which have been partially ground. This suggests that while the stones did at least offer some bonus as ballast, the primary function of them was to aid in the digestion of harder prey parts.
with many pliosaurs
Kronosaurus has been the
subject to a lot of
miscalculations about its true size. This is because when it was
first discovered pliosaurs were mostly known from skulls with very
little post cranial remains, so much of the estimates involved were a
case of making the best guess with the available material. Nearly a
century of new discoveries later and palaeontologists are now able to
produce much more accurate reconstructions, which have
subsequently seen Kronosaurus reduced in size to
ten meters long.
Despite the reduced size, Kronosaurus was still an apex predator of the early Cretaceous seas. As such Kronosaurus may have attempted to tackle a variety of creatures, although it probably had a preference for other marine reptiles like plesiosaurs that it may have had the best chance of catching. Often referred to as an Australian pliosaur, Kronosaurus may have actually had a wider geographic distribution, and other pliosaurs similar in both size and proportion to Kronosaurus are known from other areas of the world.
Basilosaurus looked nothing like the whales swimming
the oceans today.
The eel like body and narrow snout with jaws full of large conical
teeth give Basilosaurus an appearance that is
closer to the mosasaurs
of the Cretaceous, which is why it was given a name that means
‘King lizard’ by Richard Harlan in 1834. It was shortly realised
to be a mammal by Richard Owen who tried to have it renamed Zeuglodon
which means ‘yoke tooth’ in 1847, however under international
rules the first name must have priority.
Basilosaurus is thought to have grown up to an impressive eighteen meters long, bigger than any known mosasaur. This large size meant that it was probably bigger than all of the other early whales that it probably relied upon as its main food source. However despite its size and power Basilosaurus had a surprisingly weak skeletal construction of hollow vertebrae which meant that it was restricted to the upper surface waters where the water pressure would not be so great. Not a problem however when you think that the whales it preyed upon would have eventually had to come up for air, right into the predatory scope of Basilosaurus.
size estimates up to seven meters long Cretoxyrhina
is possibly the
smallest predator on the list, but those seven meters still make it
bigger than the largest recorded great white shark. Fossil evidence
suggests that Cretoxyrhina would have attacked
almost anything that was
in front of it from four meter long predatory fish to even marine
reptiles like mosasaurs and large turtles.
Key to this ferocity were the specially adapted teeth that had a much thicker than usual covering of enamel. This meant that the teeth were especially resilient to wear and damage, and could cut through anything from shell to bone almost as easily as if it were flesh. This is why Cretoxyrhina is more commonly called the ‘ginsu shark’, a nick name acquired after the famous commercial for ginsu knives that showed knives cutting through metal cans.
have been looking for evidence of giant pliosaurs for as long as they
have been known, but when they finally found one they had to piece
together a bone puzzle of around twenty thousand fragments to get an
idea of exactly how big it was. When this pliosaur first came to
the attention of the wider world it was dubbed ‘Predator X’ because
exactly what they were dealing with other than a pliosaur. Early
estimates for size that were being made while the fossils were being
slowly pieced together placed Predator X at 15 meters in length.
In time though two things, happened, the first was that the
pliosaur in question was identified as a new species of the Pliosaurus
genus, P. funkei. Second is that the 15
meters was a bit of
an over estimate, and what are now considered to be much more
accurate estimates place P. funkei at somewhere
between ten an
12.8 meters long. This however still makes P. funkei
to other large pliosaurs, and if the maximum estimate holds true,
then P. funkei may still be the largest
pliosaur. Unfortunately at
the time of this list being re-vised, only a partial skull,
paddle, and a few additional bones like vertebrae have been
identified for P. funkei.
Such large size meant that P. funkei was ‘the’ apex predator of its time, but even though the remains are so far only known from Svalbard, P. funkei probably had a much wider geographical distribution. This is because the numbers of large predators like P. funkei would need to be limited to no more than one or two in any given area as to avoid depleting the available prey, while remaining numerous enough to successfully reproduce to raise successive generations. As the top predator of its ecosystem, P. funkei would have fed upon other marine reptiles like plesiosaurs and smaller pliosaurs, as well as possibly large slow moving fish as well.
Livyatan was still alive today it would probably be
greeted with cries
of ‘Call me Ishmael’ whenever anybody saw one. You see not only
was Livyatan a huge predatory sperm whale, but
the type species name
L. melvillei is so named in honour of Herman
Melville, today best
remembered for writing the novel Moby Dick.
Livyatan is still known only from partial remains so the full size is still only an estimate. However we do know that Livyatan had teeth that were up to thirty-six centimetres long and are considered to have been the largest teeth of any predator. Additionally these teeth are in both upper and lower jaws which suggest that Livyatan was a predator of other large animals, most probably smaller whales that were very numerous at the time it swam the ocean. Such large teeth would have had a considerable advantage in taking this kind of prey as they would more easily pierce and punch straight through the blubber to hit critical areas. Additionally as a sperm whale it is not completely out of the question that Livyatan may have used echolocation (essentially sonar) to find prey that was out of sight, perhaps even locating them by their own clicks.
Livyaten seems to have suffered the same fate as many large marine predators of the Miocene to Pleistocene eras, declining with a drop of viable prey species. Today the whale closest to Livyaten in form is the sperm whale (Physeter macrocephalus), but this exists as a specialist hunter of deep water squid.
only mosasaur on the list is actually one of the last to live.
Tylosaurus swam the seas of the western interior
seaway at the end of
the Cretaceous, and was amongst the largest mosasaurs so far
discovered. The mosasaurs were reptiles like the earlier pliosaurs
and ichthyosaurs; however they developed much later and from a
different evolutionary line to the older marine reptiles. Despite
this they became the dominant oceanic predators during the last half of
the Cretaceous with the earlier pliosaurs seemingly declining in
numbers since their fossils become rarer as the Cretaceous went on.
Tylosaurus had a long eel like body that provided stable cruising speeds as well as short bursts of intense speed that it could use to take down prey. The snout of Tylosaurus is quite robust in its construction when compared to other mosasaurs which has led to the theory that Tylosaurus may have rammed other large prey so that it was stunned and could not escape while Tylosaurus turned round and finished it with its jaws. Despite the proposition of such specialist predatory behaviour however, Tylosaurus seems to have been a generalist hunter with the remains of all kinds of creatures from other marine reptiles to even sea birds being found in association with its stomach area.
has become something of a cliché to include C. megalodon
in lists of
top predators, but at the end of the day it was probably the largest
shark to ever swim in the ocean. With size estimates that vary
and twenty meters long (some even exceeding this), C.
is thought to have hunted whales when fully grown, while juveniles
were generalists that lived a life similar to other small yet fully
grown sharks until they were of a size to take down larger prey. C.
megalodon is thought to have been quite specialised in its
behaviour as it is thought to have shot up from the depths like a
rocket and slam into the bellies of whales that were near the surface
of the ocean. This idea is based upon fossil evidence of how
sometimes whale vertebrae show compression damage that seems to have
been caused by a tremendous blow from beneath.
In the end however even the devastating predatory power of C. megalodon could not help it in the face of climate change. In the twilight years of C. megalodon’s reign the oceans were cooling and sea levels were falling, events that seem to have caused the loss of pupping grounds where concentrations of C. megalodon young are known to have been. On top of this a massive reduction in the number of whales meant that there was not enough large prey to sustain the population of C. megalodon, which now found themselves to be over specialised predators that were unable to subsist on smaller prey animals that were also too quick and nimble to catch.