John Hopkins University Press is one of the publishers that has made available books for free online during this time of cancelled or remote classes. There are a some paleontology titles; each chapter can be downloaded as a PDF:
Birds of Stone: Chinese Avian Fossils from the Age of Dinosaurs
Luis M. Chiappe and Meng Qingjin
2016
https://muse.jhu.edu/book/48019
The Rise of Birds: 225 Million Years of Evolution
Sankar Chatterjee
2015
https://muse.jhu.edu/book/39108
Transylvanian Dinosaurs
David B. Weishampel and Coralia-Maria Jianu
2011
https://muse.jhu.edu/book/1874
The Rise of Marine Mammals: 50 Million Years of Evolution
Annalisa Berta
2017
https://muse.jhu.edu/book/56360
The Rise of Reptiles: 320 Million Years of Evolution
Hans-Dieter Sues
2019
https://muse.jhu.edu/book/67468
Smilodon: The Iconic Sabertooth
edited by Lars Werdelin, H. Gregory McDonald, and Christopher A. Shaw
2018
https://muse.jhu.edu/book/58589