Are there any unexplained branches of evolution?

The major thing about the fossil record (and in the biota in general) in favor of evolution is not some orthogenic-like sequences found, but the total absence of a single species that seems totally unrelated with something else - what would not be a problem at all, if species were not product of descendent with modification - such as a walking-carnivorous-tree, aquatic mammals with gills, a mammal polyp, etc.Any other imaginable origin of species would not explain the patterns of heredity that are observed. If every now and then a new species popped to existance, or a creator(s) were desiging new ones and putting them here sporadicaly (or had put them all once), wouldn't be a reasonable explanation to this pattern. Species could look totally odd from each other.If a creator or creators were really creative, they'd not need to be so repetitive, almost leading to the exhaustion the theme "tetrapod". Why not a hexapod pegasus, a gryphon, or a dragon? Could not he/they do any of that, or simply did not want to?
If the first suposition is correct, it implies a lot in the common concept of the majority of proposed creators concepts I know; if is the second which is right, is at least a bit... disappointing... all the variation that is theoretically possible, and the guy(s) do exactly what we would expect if the restriction were the restrictions of heredity mechanisms? Why? o_O

As was stated before, no one but you said that there's no evidence.There is: living beings do reproduce, and their descents are not clones of themselves, that led us to "descent with modification", unavoidable.
So, if we do not invent anything to explain the existance of actual or past's lifeforms, and knowing that there was old lifeforms, the logic suposition is that the nowadays ones are descendats of the old ones. Genetics says to us things about inheritance and the expected patterns of modification by descendance. Horses, as any other living being known, fits the expectancies. There are the fossil pattern, and the genetic pattern itself, with things like atavisms, and vestigial developments, that may disapear laterly.