According to the Encyclopedia Britannica, there are 143 species of bovids. The Animal Diversity Web is a bit less precise, indicating that there are "more than 140 extant and 300 extinct species." That second number is highly questionable because today there exist sister species that are so similar I doubt they could be told apart from fossils alone. If you check around the internet, this ~140 number comes up again and again, and Wikipedia says 143.
Research published in 2011 and later by Colin Groves, Peter Grubb, and David Leslie, which has been tagged as controversial by some but accepted by others, puts this number much higher, over 270. Why such a difference, and why is this controversy only emerging recently? It isn't like bovids are barely studied, or highly cryptic.
One of the reasons probably has to do with vagueness in the species concept itself, and it may well be the case that there are sets of species defined by Groves et al that are too finely split. But, the most likely explanation is that more modern methods, using DNA and recently developed statistical techniques, simply come up with a larger number. I've only read some of this literature, but I'm pretty sure the larger number is much closer to correct than the smaller number.
This has an important impact on understanding and addressing problems of ecology, diversity, evolution, and conservation. With respect to conservation, this means that some populations of bovids, the more rare and geographically restricted ones, are likely to be more at risk of extinction, if there are other populations at different locations that can no longer be referenced as survivors. It has been suggested, indeed, that splitting large taxonomic groups into larger numbers of species is some kind of pro conservation shenanigans. Such hippie-punching has no place in modern biology, of course. The increase in our accounted-for diversity that happens with more research is both expected from historical trends over recent decades (though it is a reverse of earlier decreases in diversity as more was learned about certain groups) and is predicted by evolutionary theory.
Anyway, I'm not here to talk about that controversy exactly. Rather, I want to point you do a new book, a really fantastic book, called Bovids of the World: Antelopes, Gazelles, Cattle, Goats, Sheep, and Relatives, by José Castelló.
Castelló uses the larger number, by the way: 271. And this book includes all of them.
The majority of this 664 page book consists of plates and a species description on the left, and details on the right, including excellent range maps, with one species in each layout. The species are divided by the usual commonly accepted tribes. This also means that many but not all of the species are grouped by very large geographical regions, because that is how the bovids are organized across our global landscape.
The back matter consists of nothing more than an index, critical in such a volume, and the front matter has an overview of what a bovid is, and details about key anatomy used in the field guide.
This book is one of a handful in the emerging subcategory of animal books that covers an entire taxonomic group either globally or nearly globally. I recently reviewed Waterfowl of North America, Europe and Asia by Reeber, which isn't quite global but since waterfowl tend to migrate is nearly so. A while back I reviewed the guide "Sharks of the World" by Compagno, Dando, and Fowler. And I've reviewed one of my favorite guides of all time, "Carnivores of the World", which covers all the carnivores except those that evolved partly into fish.
This category of book is not meant to be the one book you carry with you while touring around in the field. If you go to Africa, bring The Kingdon Field Guide to African Mammals (it includes the bovids), for example. Rather, this book is to understand the bovids as a major and important taxonomic group.
Paging through a given tribe's entries, you can come to understand biogeography better, as you see the ranges depicted on the maps of a continent or region. Also, small bovids tend to have smaller geographical ranges than larger bovids, but there are major exceptions. Why those exceptions?
Looking at the physical variation in key features, such as body size, sexual dimorphism, head dress, and markings, you can see patterns that are best explained with interesting evolutionary and ecological theories. If you teach behavioral biology or zoology, this will be a useful reference point for your thinking on all those key bovid examples. Or, if you are just interested in animals, or are planning a trip to a place where you'll be observing antelopes or other bovids, you may want to invest in this.
And when your crotchety Uncle Bob is over for a holiday dinner and you get into an argument about how many duikers there are in West Africa vs. Central Africa, you can pull out your copy of Bovids of the World and settle the bet!
The plates are drawings, not photographs, which is entirely appropriate in this sort of book. Habitats matter to photographs and that would bias the physical comparisons. Also, I can tell you from personal experience that many of the bovids, especially the forest dwellers, just don't have great photographs anyway.
I studied the information on the bovids with which I'm familiar from my own fieldwork, and I see only quality information.
As far as I know, there is not another guide like this available. Also it is not that expensive.
Table of Contents:
FOREWORD by Brent Huffman and Colin Groves 5
Sunis, Royal Antelope, Pygmy Antelope 28
Reedbucks, Waterbucks, Rhebok 38
Gazelles, Oribis, Steenbok, Grysbok, Dik-diks 82
Sheep, Goats, and relatives 302
Horse Antelopes 466
Tsessebes, Topis, Hartebeests, Wildebeests 496
Nilgai, Four-horned Antelope 542
Spiral-horned Antelopes 546
Bison, Buffaloes, Cattle, Saola 596