The planet is a Super-Earth with 1.839 Earth masses and an average surface temperature of 180.7 degrees farrenheight, the atmospheric pressure is 50 times more dense than Earth's and there's large oceans on its surface, surface gravity is 1.36 G, If life were to exist here, would its biochemistry have to be much different from Earth's life? And what traits might the animals evolve on this planet to survive?
You probably wouldn't get too far beyond insects, at least on the surface.
Assuming these lifeforms use the same protein biology as exists on earth, high temperatures would cause them to break down at above 40 C (104 F). Larger animals would have to overcome the higher gravity and the high temperature based on the square-cube law. An organism's weight is supported by its skeleton. Doubling the mass means doubling the volume, in general, which is the cube of any one dimension. Bones or chitin, on the other hand, would need to expand in cross section, i.e., the square of any dimension. After a certain limit, the skeleton, whose size increases as the square of any dimension can no longer support the mass which increases as the cube. In higher gravity, this limit is reached sooner. Not to mention the 50x higher atmospheric pressure.
The same would apply for temperature. Given the already high temperature on the planet, warm-blooded animals are out, because of basic thermodynamics. They would have to lose core heat to a hotter environment. A point here, when you say average surface temperature, what is the range? O C at the poles and 100+ C at the equator at noon? That would allow warm blooded animals at higher latitudes. Again, the other constraints mean that their size would be limited.
Flight is unlikely, as the additional energy requirements would be unfeasible to meet the effort required. Assuming pressure in a fluid is h x rho x g, given same height of atmosphere, 50x atm. density and 1.36x gravity, the animal would have to be built much heavier just to survive, which is simply additional dead weight to lift.
You would expect to find most life in water, especially in the lower depths that don't get nearly as hot. Here is where warm-blooded and multicellular organisms have a chance.The water provides uniform support to break out of the square-cube limitations and it's sufficiently cool for central heating to be an advantage. The higher levels will be plankton and bacteria that can survive higher temperatures. Much of these will be photosynthetic; they have to be, to support the remainder of the ecosystem. The next levels will be warm water plants and animals/fish, similar to those on earth. This is where we might see most reptiles. The next lower levels are where we might expect to find mammals--cool enough that warm blood is an advantage, but not so cold that the energy costs are prohibitive. Below that is regular deep sea, unless, of course, the high temperatures are due to heat from the core of the planet, rather than the sun.
The key issue here is plants/producers. Unless they are large enough to sustain subsequent consumers, nothing else will develop. You would also expect most ecosystems to develop near the largest concentrations of plants. If the thermal/gravitational environment doesn't allow more than monocellular plants or maybe some algae and fungus, your animal life is unlikely to get beyond beetles and spiders.
It's still cool enough for liquid water, so it's still in the Goldilocks Zone and as far as we know, life would be able to develop there. In fact, there are living organisms on Earth that live in comparable temperatures or even higher - the most extreme discovered so far being Strain 121, a rust-eating bacterium that thrives at 121 C inside deep-sea volcanic vents.
While the chemistry of these hyperthermophiles is naturally specialized for high temperatures in comparison to most other Earthly life (more saturated fatty acids, for instance), it isn't especially exotic and there's no reason why complex life couldn't develop with it as the norm. Even regular old Earth DNA is stable up to around 150 C.
Proteins can exist at a wide range of temperatures, but every specific kind of protein will denature at temperatures outside of its optimal range, killing the organism that requires it. In other words, organisms that evolve on a hot world will feel perfectly at home on their world but will die of cold in lower temperatures.
As for what life would look like? Well, there's no reason to think it would be fundamentally different than on any other Earth-like planet. The higher gravity would cause life to be either smaller or tougher, the thick atmosphere might make flight a bit easier, but overall evolutionary trends will be hard to predict.
Mmm. 82.61 C is a smidgen warm. Good for poilkilotherms. These are animals we inaccurately call cold-blooded like insects and reptiles. The more environment heat the faster and more active they can become. The dominant feature for life on this planet will be flight. This mainly due to the atmospheric density. The higher gravity will slow down some aspects of flight, but the higher density should more than compensate.
There is no reason to assume a planet like this wouldn't have a biochemistry too different from Earth's. However, it will display certain differences in being more heat adapted than our biochemistry. Generally the evolution of life on a planet like this will follow a similar pattern to that like ours. Species will adapt themselves to whatever environmental niches are available to be colonized.
This doesn't mean it recapitulate the same evolutionary history. You know: trilobites followed by dinosaurs followed by mammals. But there will be simpler forms followed by increasing complexity. General morphology will be lower to the ground (generally). You may need to check the basic biomechanics formulae to estimate the wingspans and limiting masses for flying creatures.
ADDED TO EDIT
Robert Freitas in his chapter on extraterrestrial biomechanics has the following useful information about alien avian lifeforms.
Exactly how do we go about designing an extraterrestrial avian? How big can they be?
On Earth, the albatross is pretty close to the maximum. This 10 kg bird has been known to achieve wingspans of up to four meters. (The most massive aerial animal that has ever lived probably weighed less than 20 kg, although there are reports of an enormously fat cock bird shot down over the Transvaal in 1892 which measured 24½ kg.360) The albatross requires a lengthy "runway" for takeoff. When it lands, it must use wing flaps like a commercial jetliner to lower the stall speed sufficiently to land safely at about 20 kph.
The primary determinant of avian size turns out to be atmospheric pressure, not gravity as many erroneously believe. It should also be pointed out that the two are unrelated. High gravity does not imply high surface pressure, as is clearly demonstrated by the members of our own solar system. For instance Venus, our sister planet, has 9000% more pressure but 12% less gravity than Earth.
A good empirical relation that seems to work well for most aerodynamic lifeforms is: S = 0.24P-1(MG)0.82, where S is total wing surface area (m2), P is air pressure (atm), M is total body mass (kg), and G is planetary surface gravity (Earth-gees).
So on high pressure worlds, alien avians can make do with vastly smaller wings. If larger wings are retained, massive bodies can be maintained aloft. An extraterrestrial with the mass of a man, standing on the surface of a one-gee, 5-atm world, could fly with the wings of an albatross. An albatross, on the other hand, could make do with less than half the original wingspan. On a 100-atm world, the 10 kg bird could be supported by stubby finlike airfoils a mere 30 cm in breadth.
Low-pressure worlds are not amenable to large avian lifeforms (Figure 11.5). Lift falls off rapidly, and nothing more massive than perhaps a small pigeon would be able to take to the air. The force of gravity plays a secondary role in fixing the size and flight characteristics of extraterrestrial bird life. On a heavy 2.2-gee planet, the wing area would have to be about 90% larger than an Earthly avian of comparable design. On a bantamweight 0.16-gee world, wing area could be reduced by as much as 80% without losing the ability to fly.
More information about avian aliens can be found here